Coronavirus: what it is and how it spreads


CONSERVATION OF ENVIRONMENTAL SPECIES

CORONAVIRUS, how can we protect ourselves


Note 1

Coronavirus, how to protect yourself

Television, radio and newspapers inform us daily on the development of the situation in our country and in the rest of the world about the coronavirus pandemic that has hit the whole world, also providing us with valuable information on the personal protection measures to follow. In any case, the main rules indicated are:

  • stay at home as much as possible and leave only on the basis of what we are told by the competent state bodies;
  • wash your hands often;
  • avoid close contact with other people;
  • avoid hugs and handshakes;
  • always keep a distance of at least one meter with other people;
  • sneezing or coughing into a disposable handkerchief avoiding getting it in the hands;
  • do not use glasses, bottles, cutlery or plates used by others;
  • do not touch your eyes, nose and mouth with your hands;
  • do not take antiviral drugs and antibiotics, unless they are prescribed by the doctor;
  • regularly clean the surfaces with chlorine-based disinfectants (bleach) or alcohol;
  • if you think you are sick or you are assisting sick people, always use masks;
  • if you suspect that you are ill, you must stay at home, not go to the emergency room or medical offices but call your family doctor or pediatrician or the emergency medical service on the phone. Alternatively, the toll-free number of your region which can be found listed at this link Covid-19 - Regional toll-free numbers.
Of course, knowing what it is, common sense can tell each of us how to behave and not panic.

Our government has prepared a series of guidelines to follow, in the public and in the private sector, to try not to get sick and to contain the infection.

The first rule to follow is to take care of hygiene and in particular to wash your hands thoroughly with soap and water for at least 60 seconds. Soap is important because since the virus is formed by an outer lipid (fat) layer, the soap dissolves the fat, killing the virus. If soap cannot be used, an alcohol-based hand sanitizer (ethyl alcohol) at a concentration of at least 60% can be used.

So let's see the indications that the National Institute of Health of our country provides us on how to take care of the hygiene of our hands.

If necessary to use the mask, the following rules must be followed:

  • before putting on the mask, wash your hands with soap and water or an alcoholic solution;
  • cover the mouth and nose well with the mask, making sure it is intact and adheres well to the face;
  • avoid touching the mask while wearing;
  • when it becomes wet it must be replaced;
  • the mask must be removed by taking it from the elastic and without touching the front and thrown into a closed bag;
  • wash your hands after taking it off.

Following strict hygiene rules is essential to avoid contracting the coronavirus.

Aid for the most vulnerable people

For frail people throughout the national territory, services are available home delivery of medicines. You can contact the toll-free number 800 06 55 10 (active 24 hours a day and 7 days a week), which in turn contacts the nearest Red Cross which will take action to have the necessary drugs directly in your home. The service is free.

Individual regions, individual municipalities and the municipal police publish a list of shops they carry out home delivery of groceries. Consult the website of your Municipality for all the relevant information.

If for reasons of necessity you are forced to leave your home, bring with you the self-declaration form for movements prepared by the Interior Ministry, which can be downloaded from this page Self-declaration form for movements of the Interior Ministry updated on 26 March 2020.

How to make a disinfectant to counter the coronavirus

To make an effective disinfectant against coronavirus, Matteo Guidotti, researcher at the "Giulio Natta" Institute of Chemical Sciences and Technologies of the National Research Council (Cnr-Scitec) in Milan, explains that 70% ethyl alcohol or 0.5% hydrogen peroxide or 0.1% sodium hypochlorite (the common bleach). Since homemade products are too concentrated, they must be diluted and the following disinfectant solutions can be prepared:

1. Alcohol-based disinfectant

  • 400 ml of denatured alcohol at 90% (the pink one on the market), which corresponds to about two full plastic cups;
  • tap water, up to a total of half a liter.

    This solution, explains Guidotti, "can take up to a week".

2. Disinfectant based on hydrogen peroxide

  • 500 ml (equal to about half a plastic cup) of 3% hydrogen peroxide for dressing (10 volumes);
  • tap water, up to half a liter of disinfectant solution.

  • This solution must be prepared every day because the active ingredient degrades after 24 hours.

3. Disinfectant based on bleach

  • 10 ml of 5% bleach (about a soup spoon);
  • tap water up to half a liter.

  • This solution must be prepared every day "because the active principle is not stable beyond 24 hours

It should be noted that these disinfectant solutions are to be used to clean and disinfect the surfaces of the house and not for body and personal care.

Bibliographic sources


Higher Institute of Health
Ministry of Health
Scientific American, February 5, 2020.
Science Almanac

Note

1. Image from CDC Center for Disease Control and Prevention courtesy of Alissa Eckert, MS, Dan Higgins, MAMS


It is expected that you can test positive for the coronavirus even after the vaccine

News about people who tested positive for the coronavirus despite having vaccinated often emerge in newspapers, social networks and in WhatsApp groups, with the risk of causing some misunderstanding about the functioning and usefulness of vaccines. It is possible, although it seems relatively rare for now, to get a positive molecular test result for the coronavirus even weeks after vaccination, and that doesn't mean that something has gone wrong.

It depends on the very functioning of the vaccines, which ensure that in the event of a coronavirus infection the immune system is ready to protect almost 100 percent from severe forms of COVID-19, in the case of those so far authorized in the West. But each person is unique, and the same goes for our immune systems that respond differently to the vaccine. It may therefore happen that any infection develops enough to be detected by tests, although at the moment we do not yet know how often. Preliminary data from countries where the campaign is further ahead, however, are also encouraging on the effectiveness of protection from asymptomatic infections. In this phase of the pandemic, in any case, the important thing is to avoid that there are full hospitals around the world every day and tens of thousands of deaths from the effects of the disease.

You can be positive without being sick
The first thing to remember is that having coronavirus does not imply that you necessarily fall ill with COVID-19. In a pandemic year we have learned that many people are infected and remain positive for some time, but do not develop symptoms. In the initial phase of the infection they can infect other people, probably to a lesser extent than those who develop symptoms.

You can test positive weeks after the vaccine
We currently know that vaccines protect against COVID-19, but we don't know to what extent they reduce the risk of getting infected. It can happen, and is happening all over the world, that a fully vaccinated person becomes infected: the vaccine is not some kind of inviolable and invisible barrier against the virus, and it does not have the exact same effect on every person. What it does, however, is to prepare the immune system so that in case of contact with the coronavirus it acts by preventing the development of symptoms or at least serious ones.

But it can happen - it is expected - that the immune system of some vaccinated people is still unable to stop any infection so quickly as to prevent it from being detected by a possible test. To understand how frequent it is, and with what percentage vaccines protect even from simple asymptomatic or paucisymptomatic infections, further studies are needed. But the first data from countries where the campaigns are particularly advanced, however, are also encouraging as regards the protection against asymptomatic infections, which seem drastically reduced by vaccinations. According to Pfizer, data on administration of its vaccine in Israel suggest that it protects against asymptomatic infections with 94 percent effectiveness.

There remains the possibility that a vaccinated person who comes into contact with the virus, and that although asymptomatic was subjected to the swab, for example for an activity of screening, can be positive. The sensitivity of the tests, especially the molecular ones, is such that they can detect the presence of the genetic material of the virus even if present in limited quantities (low viral load). News on similar episodes, especially if sporadic, should not frighten or worry about the effectiveness of vaccines.

The vaccine doesn't work right away
Depending on the type of vaccine received, then a few days or weeks must pass before the vaccination takes effect. In this period of time, there is the possibility of still falling ill with COVID-19 simply because the body has not yet had time to develop an immune response to the vaccine. You can also get sick if you had been infected a few days before vaccination, and the infection was therefore already underway.

In this circumstance it is completely normal that COVID-19 can develop, as it happens with other diseases if the pathogens that cause them are contracted before the vaccine to counter them has activated the immune response.

Coronavirus vaccines authorized so far also require the use of two doses, administered a few weeks apart. The efficacy of Pfizer-BioNTech's vaccine, for example, is around 52 percent after the first dose and reaches around 95 percent in the days following the second administration. Let's talk about effectiveness in general against COVID-19: it is good to reiterate that the effectiveness against severe forms of the disease is around 100 percent for all vaccines so far authorized in the West.

The vaccine does not test positive
There is no chance that you will be positive in a molecular test (swab) due to vaccination. Vaccines help the immune system recognize certain characteristics of the coronavirus so that it learns to counter them, without having to come into contact with the virus itself.

You can get sick even if you are vaccinated
As we have seen, all vaccines authorized so far protect against severe forms of COVID-19, while their effectiveness against the disease in general varies depending on the type of vaccine, albeit remaining very high.

In some rare cases it can therefore happen that a vaccinee falls ill with COVID-19, but without the risk of developing serious symptoms that could require hospitalization. Each of us is made differently and it is normal for us to react differently to vaccination, as well as to the conditions that can lead to an infection.

We do not know if and how much vaccinated people are less contagious
Coronavirus vaccines have been in use for just over three months, and it is therefore still early to know if they are able to reduce the circulation of the coronavirus. Data and clues collected so far, especially from countries where a lot of vaccinations are being made like Israel, are encouraging, but it will take a few more months to get a better idea.

With some vaccines, the immune system learns not to make us sick, but it does not develop the ability to prevent an infection from occurring that makes us contagious anyway: what is called "sterilizing immunity" does not occur. In the absence of sterilizing immunity, the pathogen continues to circulate among the population, and can cause new infections and possibly the appearance of the disease. In some circumstances it can also change over time, becoming more resistant to the immune defenses.

The most common flu vaccine uses inactivated viruses, but does not lead to a true sterilizing immunity, because it does not induce a localized immune response in the respiratory tract (through which the virus spreads and then infects other individuals). This and the fact that the immunization rate is relatively low (usually just under 50 percent among adults), as well as the virus's ability to adapt easily to other species, causes influenza viruses to change continuously and partially escape the control of our immune system. The consequence is that, depending on the years, vaccination campaigns prove to be more or less effective, still allowing enormously reducing the workload for hospitals and saving millions of lives.

In general, however, the risk of contagion increases as the viral load in the body increases. Vaccines help to keep it low and therefore reduce the risk of a positive spreading a high number of viral particles by breathing and speaking, which could then cause the contagion of those in the vicinity (especially in closed environments).

In conclusion
If you hear news about someone who got vaccinated and still tested positive for a molecular test weeks later, don't be alarmed. While we are waiting to better understand if they prevent new infections, we know for sure that coronavirus vaccines protect against severe forms of COVID-19 and can therefore save millions of lives.

Pending confirmation on the reduction of contagiousness, the use of masks and physical distancing remain good practices both for the vaccinated and for those who have not yet received the vaccine, or will not be able to do so for other health reasons.


Covid, how the virus spreads in the air indoors. Home, premises, school: the study of scientists in the graphics of El Pais

The simulations of a group of scientists, led by Professor José Luis Jiménez (expert in chemistry and dynamics of air particles from the University of Colorado)

How to spreads the coronavirus in the air in Closed places? And how can the contagion be reduced by using prevention measures such as a mask and ventilation of an environment? The graphics of an article published by El Pais.

The article analyzes three very common situations: one home visit of relatives or friends, a lunch in a restaurant crowded and one lesson in the classroom. To calculate the probability of contagion, El Pais used the simulations of a group of scientists, led by Professor José Luis Jiménez (expert in chemistry and dynamics of air particles at the University of Colorado) (Photo: El Pais).

In the first case, we examine what happens in a living room with 6 people, one of which is infected. After four hours without any precautions, they would all be infected (Photo: El Pais)

If those present used the masks, the risk would be reduced to four infections. The masks Sunglasses indeed they are not enough if the exhibition indoors is very long, explains the Spanish newspaper (Photo: El Pais)

The risk of contagion is reduced below a person when the group uses the masks, reduces the duration of the meeting by half and then ventilate the room (Photo: El Pais)

To worry in closed places is the possible contagion from aerosol, those tiny particles that a person expels while breathing and speaking that remain suspended in the air (Photo: El Pais)

Without ventilation of the closed environment, these particles remain suspended in the air and condense in the room with the passage of time (Photo: El Pais)

The graphics emphasize the risk of contagion in a closed place if let's talk, we shout or let's sing. In these cases, in fact, we emit a lot potentially infectious particles. These particles, if not diluted with ventilation, concentrate over time, increasing the risk of contagion (Photo: El Pais)

The most explosive situations, however, are those of Cafe is restaurants crowded, explains El Pais. The graphics show the example of a bar that has reduced its capacity by half, with 15 customers - one of them infectious - and three employees. The doors are closed and there is no ventilation (Photo: El Pais)

After four hours without any measure according to this simulation, all the other 14 customers are infected (Photo: El Pais)

Still after four hours, but assuming everyone is wearing the mask, the infection would be reduced to 8 people: still not enough (Photo: El Pais)

Applying proper ventilation of the environment, also using i conditioners, and if the time spent at the bar shortens, the likelihood of contagion decreases to one person (Photo: El Pais)

The last example analyzed is that of a 'classroom with 24 pupils and a positive teacher (Photo: El Pais)

According to the Pais elaboration, the most dangerous situation is in fact that of a positive teacher in a'classroom without ventilation: if the pupils spent two hours in the classroom without taking any preventive measures, the contagion could reach up to 12 students (Photo: El Pais)

If everyone in the classroom used the masks, but remaining without ventilation, the risk would be reduced to 5 students (Photo: El Pais)

The risk is almost totally canceled out if during class the classroom also comes airy and if we stop after an hour to completely renew the air (Photo: El Pais) (source SKY article)


Bread, cured meats and coronavirus: how to deal with these foods? The precautions explained by Antonello Paparella

After publication of our interview with Professor Antonello Paparella * on the precautions to be taken in the kitchen to avoid the presence of the coronavirus, many have asked for clarification for some foods. Below we publish two comments and Professor Paparella's answer.

Today I went to get the bread and the baker had cold / flu symptoms, so as not to embarrass her I took the bread I asked for but I think I'll leave it in the car a couple of days and then throw it away. The question: on bread and other elements, how long can such viruses remain active? Is it advisable to increase the consumption of canned foods over fresh ones?

Yesterday in the family we were wondering if it is appropriate to consume mozzarella or any other food that is subject to manipulation by an operator of the business in which the purchase, for example the cold cuts and which are then not subjected to capture nor can be carefully washed like fruits and vegetables. If during the packaging of the operator's saliva droplets somehow settle on the food, I take it home, handle it and then what? The same can be said for bread. In many regions it is still bought in bulk at the bakery, it is taken (with gloves) and bagged by the clerk. What do I do touch it after a few hours? Do I put it in the oven and eat it toasted? What Hamlet doubts!

Below is the opinion of Professor Antonello Paparella

The data obtained so far on the persistence of this coronavirus in the environment refer almost exclusively to research carried out previously on other coronaviruses, conducted on inert materials such as steel, plastic, glass, gloves and gowns. The persistence of a virus on a material depends primarily on the type of virus and, within the same type of coronavirus, it can be different from one strain to another. For example, the P9 and GVU6109 strains of the SARS-CoV virus demonstrated different persistence on paper, 4-5 days and 1 day, respectively. In foods, the behavior may not be the same and, at present, there is no evidence that foods can play a role in infection with this SARS-CoV-2 coronavirus.

The data so far collected in China and Italy indicate that the infection spreads rapidly and is likely to happen, as with other respiratory infections, through the dissemination of respiratory secretions from person to person in close contact and not through food. If persistence on foods were to be demonstrated, given that investigations to this effect are underway, it is more than likely that this path of infection is the exception rather than the rule.

Foods are "living systems", containing nutrients and moisture, and are inhabited by a microbial community that influences the evolution of the physical and chemical characteristics of the food over time. This means that during the commercial life of a food product, the survival of each microorganism, including viruses, is conditioned by a series of factors which are necessarily different from inert materials. All these characteristics could make life more difficult for the virus, particularly if time passes from purchase to consumption and if there is further handling at home, for example when we put the bread in the bag or cut it and then remove part. surface microorganisms with cutting or crumbling.

The same thing it can happen when we buy cold cuts and cheeses that are generally handled by the operator using gloves, are not easily exposed to contact with respiratory secretions and in any case are not usually consumed immediately after purchase. If the estimated food risk for this SARS-CoV-2 virus is very low, even more remote is that from foods such as bread or cold cuts.

The one on which we should instead pay more attention are handles, money, shopping carts, the interior surfaces of a bus, elevator or ATM buttons and all those objects that come into contact with many hands and can accidentally be exposed to the risk of contamination recent with respiratory secretions. In all these cases, remember not to touch your face (in particular mouth, nose, eyes) with improperly sanitized hands and always keep a disinfectant solution in your pocket, even when shopping, to be used after touching surfaces that could be contaminated.

* Professor of Food Microbiology at the University of Teramo

** Respiratory virus that spreads mainly through close contact with a sick person. The primary route is the droplets of the breath of infected people for example through: saliva, coughing and sneezing direct personal contact hands, for example by touching with contaminated hands (not yet washed) mouth, nose or eyes.

To know the number of people affected in Italy Click here

To know the number of people affected in the world click here


What the coronavirus does to our body

The efforts of virologists, epidemiologists, researchers and doctors to seek treatments and to develop a vaccine against the coronavirus epidemic (SARS-CoV-2) result in the publication of thousands of scientific research and clinical reports every week. The site of Science, one of the most prestigious scientific journals in the world, has collected the most relevant observations and discoveries on COVID-19, showing how the current coronavirus proves to be extremely aggressive in about 5 percent of patients, causing very serious symptoms. The disease mostly affects the lungs, but researchers and doctors have noted important effects on much of the rest of the body, from the brain to the toes.

Lungs
Coronavirus is transmitted mostly through the small drops of saliva that we emit by talking or coughing. The main route of contagion is through the upper respiratory tract: throat and nose. In the latter's cells, the virus seems to be particularly at ease: their cell membranes are rich in ACE2 (angiotensin converting enzyme 2), a receptor that regulates what can and cannot enter the cell. ACE2 is quite widespread in the cellular tissues of our body and this could explain why the coronavirus is able to do widespread damage: with proteins in its envelope, it tricks ACE2 to inject its own genetic material (RNA) into the cell and exploit it to replicate thousands of times, with new copies that will then infect other cells.

As replication occurs, infected individuals become contagious, especially in the first week from the moment of infection. They may develop extremely mild symptoms - even to the point of not realizing they are sick - or fever, dry cough, loss of smell and taste, joint pain, headache and sore throat. In the event that their immune system fails to get rid of the coronavirus, it continues its invasion by reaching the deepest parts of the respiratory system: the lungs.

The smallest and most delicate structures in the lung are the alveoli, the place where the exchange of oxygen and carbon dioxide in the bloodstream takes place. The cells of our body in fact need oxygen to live and manage their processes, which lead to the production of carbon dioxide which must instead be eliminated with the air we exhale. The very thin layer of cells that makes up the alveoli is rich in ACE2, and this favors the coronavirus.

The immune system reacts to the infection with its primary resources through chemokines, molecules which in turn activate the response of other immune cells that target the cells infected with the virus and destroy them. It is a very violent reaction and comparable to the effect of a carpet bombing: after their passage, dead cells and fluids remain, on which bacteria can produce (pus). For the patient, the symptoms of this battle are typical of pneumonia: fever, cough and progressive difficulty in breathing normally.

Many patients are able to overcome this phase of COVID-19 on their own, by taking drugs to control certain symptoms or with the help of oxygen to facilitate breathing. In severe cases, however, the disease progresses and respiratory distress syndrome develops: oxygen levels in the blood drop significantly and breathing becomes increasingly difficult. In CT scans and radiographs, the lungs appear with opacity, where they should instead appear dark indicating the presence of air. Intubation in intensive care is necessary for patients in these conditions. Many of them die: the alveoli become clogged with fluids, mucus, dead cells and other material and do not allow the exchange of oxygen with the blood.

Several doctors have also reported that in the most serious patients a “cytokine storm” sometimes develops, that is, an over-measure reaction of the immune system that is much more destructive in the lung tissues. Some pulmonologists are not so sure that the phenomenon is very recurrent and call for some extra caution, because the drugs used to reduce these oversized reactions reduce the reactivity of the immune system, with the risk that in the meantime the coronavirus can flourish. and to carry on the infection.

Heart and blood circulation
In recent weeks, it has become evident that COVID-19 affects various other parts of the body in addition to the lungs, also entailing important risks for the heart. It is not yet clear how the coronavirus affects the cardiovascular system, but by now dozens of research and clinical reports report consistent damage that is quite common, among serious patients. A study carried out in Wuhan, the Chinese city where the pandemic began, indicated that about one fifth of 416 patients examined with COVID-19 had reported heart damage. Another research, carried out in hospitals in the same city, reported the presence of irregularities in the heartbeat (arrhythmias) in 44 percent of 138 hospitalized patients.

Other doctors and researchers have reported the presence of blood clots, which form in the blood vessels due to inflammation. Our body has systems to dissolve these clots, but in some cases small fragments do not break down and continue to circulate. At the level of the lungs, these lumps can block important vessels leading to pulmonary embolism, which can be lethal. Other clots can travel to the brain, causing permanent damage.

Coronavirus infection can also induce a reduction in the width (lumen) of blood vessels. Several studies report clinical cases of patients with forms of ischemia in the toes and hands: the reduced blood circulation in these peripheral areas leads to swelling and pain in the fingers, and in the most severe cases to permanent damage to their cellular tissues. Other damage occurs at lung levels, complicating situations that are already quite compromised in severe patients.

COVID-19 is increasingly turning out to be not only a pulmonary but also a cardiovascular disease, and researchers have not yet understood its causes and dynamics. One hypothesis is that also in this case the presence of ACE2 on the walls of blood vessels and the heart favors the presence of the coronavirus. There could also be a simpler explanation linked to the fact that severe lung damage affects the rest of the cardiovascular system, which is closely related to the pulmonary system. A better understanding of these mechanisms will be essential to find more effective treatments for the disease.

Kidneys
A study conducted in Wuhan on 85 patients showed that about a quarter had suffered from severe forms of kidney failure. In un’altra ricerca, condotta su 200 pazienti ricoverati, sono state riscontrate nel 59 per cento dei casi proteine e sangue nelle urine, una condizione che si verifica quando i reni non riescono a filtrare adeguatamente il sangue che li attraversa. Gli individui con precedenti problemi renali seri si sono inoltre rivelati più esposti al rischio di morte dopo avere contratto il coronavirus.

Non è chiaro se e come il coronavirus attacchi direttamente i reni. Per ora gli studi in tema sono scarsi, anche se una ricerca svolta conducendo autopsie sui pazienti ha consentito di rilevare la presenza di tracce del virus nei tessuti renali. L’insufficienza renale potrebbe essere comunque dovuta più in generale ai forti stress cui è sottoposto l’organismo dei malati: l’intubazione è un fattore di rischio per i reni, così come lo sono l’assunzione di farmaci molto pesanti, come gli antivirali che vengono somministrati per rallentare la replicazione del virus.

Nei primi mesi della pandemia ci si è concentrati molto sui ventilatori, essenziali per aiutare i pazienti gravi a respirare e a tenerli in vita, in attesa che il loro sistema immunitario riesca a sbarazzarsi del coronavirus. Diversi medici segnalano nelle loro ricerche l’importanza di dotare gli ospedali di un maggior numero di macchine per la dialisi, terapia che serve a ripulire il sangue da scorie e tossine, nel momento in cui un’insufficienza renale non permetta all’organismo di farlo autonomamente. Una maggiore disponibilità di questi macchinari potrebbe rivelarsi essenziale per salvare la vita di alcuni pazienti gravi.

Cervello
Un’infezione da coronavirus può anche comportare danni importanti a livello neurologico, soprattutto a carico del sistema nervoso centrale. Sono stati segnalati casi di encefaliti (infiammazioni del cervello) e di ictus. Il sistema nervoso centrale è relativamente isolato dal resto dell’organismo, proprio per proteggerlo dagli attacchi degli agenti esterni, e per ora non è chiaro in che misura il coronavirus possa creare danni. Un’indiziata è la presenza di ACE2 nella corteccia cerebrale, ma non ci sono per ora molti elementi in letteratura scientifica.

Uno studio condotto in Giappone ha evidenziato la presenza di tracce del virus nel liquor, il fluido cerebrospinale nel quale galleggia il sistema nervoso centrale. La ricerca è però basata sulle analisi di un solo paziente, che aveva sviluppato encefalite e meningite.

I dati sugli effetti per il cervello della COVID-19 sono ancora molto scarsi, e per questo alcuni neurologi stanno organizzando collaborazioni internazionali per raccogliere informazioni sui pazienti, con l’obiettivo di avere un quadro più preciso della situazione.

Intestino
Diverse ricerche segnalano che il coronavirus riesce a raggiungere anche le parti inferiori del sistema digestivo, dove c’è un’abbondanza di ACE2. In circa la metà delle feci di pazienti con COVID-19 analizzate in uno studio è stata rilevata la presenza di tracce del virus. Un’altra ricerca ha consentito di identificare tracce del coronavirus nelle cellule del retto, del duodeno e di altri tratti intermedi dell’intestino. Questa presenza spiegherebbe perché circa un quinto dei malati di COVID-19 abbia ricorrenti episodi di diarrea.

Altri sintomi
Fino a un terzo dei pazienti ricoverati sviluppa una fastidiosa congiuntivite, un’infezione dell’occhio, anche se non ci sono ancora elementi chiari per capire se e come il coronavirus colpisca direttamente gli occhi. Altri sintomi indicano forti stress per il fegato, anche se in questo caso la causa potrebbero essere i farmaci per rallentare l’avanzamento dell’infezione o più in generale il forte stress che il coronavirus comporta per il sistema immunitario.

Tempo e cautele
Saranno necessari mesi, probabilmente anni, prima di avere conoscenze più approfondite e chiare sulla COVID-19 e gli effetti del coronavirus sul nostro organismo. La maggior parte degli studi diffusi finora sono in formato preprint, quindi pubblicati direttamente dai ricercatori senza che sia effettuata una verifica da loro colleghi alla pari. È una condizione inevitabile per rendere disponibili il prima possibile nuovi elementi alla comunità scientifica, ma questo implica che siano assunte cautele in più nel riferirne i contenuti: alcune evidenze potrebbero essere smentite, e altre potrebbero essere integrate con nuovi elementi.


Come il Coronavirus attacca le cellule

Di Cristina Marrone

I polmoni di un ragazzo di 28 anni ricoverato in terapia intensiva. Il velo nebuloso bianco и indice della polmonite.

Per buona parte dei pazienti il Covid-19 inizia e finisce nei polmoni, perchй, come l’influenza, i coronavirus sono malattie respiratorie. Si diffondono tipicamente mediante la tosse e gli starnuti delle persone infette, attraverso le micro gocce che possono trasmettere il virus ai soggetti che si trovano a stretto contatto. Anche i coronavirus si manifestano con sintomi simili a quelli tipici dell’influenza, per questo le due malattie possono essere confuse: i pazienti possono presentare dapprima febbre e tosse, che progrediscono poi diventando polmonite interstiziale.

In che modo questo coronavirus causa l’infezione?
Il virus si diffonde attraverso le goccioline diffuse nell’aria da tosse o starnuti di persone infette che, chi и vicino, puт assorbire attraverso naso, bocca o occhi. Le particelle virali in queste goccioline viaggiano rapidamente verso la parte posteriore del naso e verso le mucose all’interno della gola, attaccandosi a un particolare recettore nelle cellule. Il nuovo coronavirus ha tante punte che ricordano quelle delle corone. Le punte sono formate da «peplomeri» strutture proteiche che insieme ad altri meccanismi servono al virus per attaccarsi alle cellule dell’organismo da infettare. Una volta che si sono legati alle cellule ospiti, i virus rilasciano il loro codice genetico modificando il comportamento della cellula.

In che modo questo processo causa problemi respiratori?
Le copie del virus si moltiplicano, esplodono e infettano le cellule vicine. I primi sintomi spesso partono dalla gola con mal di gola e tosse secca. Poi il virus striscia progressivamente lungo i bronchi. Quando il virus raggiunge i polmoni, le loro mucose si infiammano. Ciт puт danneggiare gli alveoli o le sacche polmonari che devono lavorare di piщ per svolgere la loro funzione di fornire ossigeno al sangue che circola in tutto il nostro corpo e rimuovere l’anidride carbonica dal sangue. Il gonfiore e il flusso alterato di ossigeno possono far riempire quelle aree dei polmoni con liquido, pus e cellule morte causando polmonite. Proprio a causa di questa degenerazione alcuni pazienti accusano gravi problemi respiratori, tanto che devono essere ricoverati in terapia intensiva e ventilati. Nei casi peggiori, quando si verifica la sindrome da distress respiratorio acuto, i polmoni si riempiono a tal punto di fluido che nessun supporto respiratorio puт aiutare il paziente, che non riesce piщ a respirare e muore.

Quale traiettoria prende il virus nei polmoni?
Il dottor Shu-Yuan Xiao, professore di patologia presso la School of Medicine dell’Universitа di Chicago e direttore del Center for Pathology and Molecular Diagnostics presso l’Universitа di Wuhan, intervistato dal New York Times, ha esaminato i rapporti sul decorso patologico dei pazienti con coronavirus in Cina. Ha spiegato, ma si tratta ancora di ipotesi, che l’infiammazione causata dal virus sembra partire lentamente nelle aree periferiche su entrambi i lati del polmone per poi propagarsi (mettendoci anche del tempo) verso il tratto respiratorio superiore, la trachea e altre vie aeree centrali, dove in un primissimo momento non si manifestano sintomi. Questo decorso potrebbe spiegare perchй a Wuhan, dove и iniziato l’epidemia, molti dei primi casi non sono stati identificati immediatamente. I test svolti all’inizio in molti ospedali cinesi non hanno sempre rilevato un’infezione nella parte periferica dei polmoni quindi, alcune persone che manifestavano sintomi, sarebbero state rimandate a casa senza trattamento, e avrebbero poi cercato cure in altri ospedali o restando a casa, infettando cosм il resto della famiglia. «Questo и uno dei motivi per cui c’и stata una diffusione cosм ampia» ipotizza lo scienziato.

Cosa succede ai polmoni?
Il Professore associato della University of Maryland School of Medicine Matthew B. Frieman, che studia i coronavirus altamente patogeni, intervistato dal National Geographic, ha spiegato che nei primi giorni dell’infezione il nuovo coronavirus invade rapidamente le cellule dei polmoni umani che sono di due tipi: quelle del primo tipo producono muco, le altre sono dotate di strutture simili a capelli, e sono pertanto chiamate ciliate. Il muco quando viene espulso, aiuta a proteggere i tessuti polmonari dai patogeni e assicura che gli organi preposti alla respirazione non si secchino. Le cellule ciliate hanno il compito di «scuotere» il muco, eliminando corpi estranei come pollini o virus. Frieman spiega che la SARS infettava e uccideva le cellule ciliate, che infine si staccavano, riempiendo le vie aeree del paziente con residui e fluidi, e ipotizza che lo stesso stia succedendo nel caso del nuovo coronavirus. E questo sarebbe il motivo per cui molti pazienti sviluppano la polmonite da entrambi i polmoni

Qual и il ruolo del sistema immunitario?
Nella seconda fase della malattia entra in gioco il sistema immunitario. Allarmato dalla presenza di un’invasione virale, il nostro organismo si impegna a combattere la malattia inondando i polmoni con cellule immunitarie che hanno il compito di eliminare il danno e riparare il tessuto polmonare. Quando lavora correttamente, questo processo infiammatorio и rigorosamente controllato e confinato solo alle aree infettate. Ma a volte il sistema immunitario va in tilt e queste cellule uccidono tutto quello che incontrano, incluso il tessuto sano. La risposta abnorme del nostro sistema immunitario puт provocare piщ danni che benefici, e su questo concordano i medici e, nel caso del coronavirus, sempre piщ residui intasano i polmoni e la polmonite peggiora sempre di piщ. Nella fase finale il danno ai polmoni и cosм serio che puт sopraggiungere la morte per insufficienza respiratoria e, in alcuni casi, i danni ai polmoni sarebbero permanenti. L’infiammazione rende piщ permeabili anche le membrane tra le sacche d’aria e i vasi sanguigni, il che determina l’ingresso di fluido nei polmoni, compromettendo la loro capacitа di ossigenare il sangue. Nei casi gravi, praticamente l’organismo riempie i polmoni di liquidi e non si riesce a respirare. Le persone muoiono cosм.

Che cosa sono i fori a «nido d’ape» nei polmoni?
Uno studio recente condotto da un team guidato da ricercatori della Icahn School of Medicine Mount Sinai ha rilevato che oltre la metа di 121 pazienti esaminati in Cina avevano radiografie toraciche normali all’inizio della loro malattia. Quando la malattia progredisce, le scansioni TC mostrano opacitа, una sorta di velo nebuloso in alcune zone del polmone tipiche di infezioni respiratorie virali. Quelle aree opache possono ispessirsi quando la malattia peggiora, creando quello che i radiologi chiamano formazione di fori «a nido d’ape». Questi fori sono probabilmente creati dalla risposta iperattiva del sistema immunitario, che crea cicatrici che proteggono e irrigidiscono i polmoni.

Che cosa non sanno ancora gli scienziati dei pazienti con coronavirus?
Non si conoscono ancora molte cose. Sebbene la malattia assomigli alla SARS per molti aspetti e abbia elementi in comune con influenza e polmonite, il decorso della malattia non и ancora del tutto chiaro. Alcuni pazienti possono rimanere stabili per oltre una settimana e quindi sviluppare improvvisamente la polmonite. Altri pazienti sembrano riprendersi, ma poi sviluppano nuovamente i sintomi. Alcuni pazienti in Cina si sono ripresi ma si sono ammalati di nuovo. Ricadute in alcuni casi, il virus era ancora in circolo e non era stato rilevato dal tampone. Ma in altri casi i pazienti avevano un tessuto polmonare danneggiato e vulnerabile, che и stato attaccato in un secondo momento da batteri . Alcuni di questi pazienti hanno finito per morire per un’infezione batterica, non per il virus, anche se questa и una circostanza rara. Altri casi sono misteri . Il dottor Xiao ha raccontato di aver conosciuto personalmente un uomo e la moglie che erano rimasti contagiati, ma sembrava stessero migliorando. L’uomo ha cominciato perт a peggiorare ed и stato ricoverato in ospedale. Si trovava in terapia intensiva, stava ricevendo ossigeno e ma aveva scritto a sua moglie che stava migliorando, aveva buon appetito e cosм via. Nel tardo pomeriggio la donna ha perт smesso di ricevere messaggi. Non sapeva cosa stesse succedendo. E alle 10 di sera, ha ricevuto un avviso dall’ospedale che le comunicava che il marito era morto.


La rapidità della reazione

Quello contro virus e batteri, allora, è il vero fronte caldo della medicina moderna. «Lo scenario attuale poggia su un mix particolare: flussi inarrestabili di viaggi e migrazioni, un Pianeta sempre più popolato, sfruttato e inquinato, giganteschi allevamenti di animali veicoli di virus in Asia e situazioni di promiscuità, sempre in Asia e in Africa, dove ancora si vive a contatto con animali selvatici e in condizioni di igiene precarie» spiega Barbara Gallavotti, biologa e autrice del saggio Le grandi epidemie (Donzelli). «A tutto questo si aggiunge il problema dei batteri sempre più resistenti agli antibiotici. Ma non possiamo pensare di vivere in una bolla: il contagio con i microrganismi sarà continuo e inevitabile. La sfida, allora, si vince sulla velocità di reazione e sulla capacità di fare rete».

Il pensiero corre ancora alla Sars che tra il 2002 e il 2003 ha contagiato 8.000 individui, uccidendone 750. «E proprio il paragone ci fa capire che stiamo gestendo meglio questa emergenza» rassicura la biologa. «All’epoca il problema fu nascosto e sottovalutato. Ora il meccanismo di contenimento è scattato in fretta. Sono partiti controlli a tappeto sulle persone e protocolli con regole sugli spostamenti e i trattamenti medici». In Italia, nella task force, operano in sinergia ministero della Salute e Istituto superiore di Sanità, carabinieri dei Nas, uffici di sanità marittima, aerea e di frontiera e altri ancora, in strettissimo contatto con l’Organizzazione Mondiale della Sanità e il Centro europeo per la prevenzione e il controllo delle malattie.

«Anche la scienza ha fatto passi da gigante: il primo focolaio della Sars è stato registrato a novembre 2002, ma il virus venne identificato oltre 4 mesi dopo. Adesso gli esperti hanno già sequenziato il Dna della polmonite cinese e diffuso la mappatura sul sito Gene-Bank, a cui hanno accesso tutti i ricercatori del mondo, che si sono immediatamente messi all’opera. Sembra fantascienza, ma è realtà e in futuro i progressi tecnologici ci daranno ricerche ed esami ancora più veloci ed efficaci. È come se, in una partita, noi conoscessimo l’identikit e le mosse dell’avversario: lo puoi tenere sotto controllo. E vincere diventa più fattibile».

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