Published: 24.03.2020
To date, there are hundreds of coronavirus cases in the Czech Republic. The whole country is under a lockdown and no one can tell how the situation will further develop. The whole world is combating the virus. And people keep asking when we will control the virus. “I believe that Europe will control the virus in two or three months. The number of people who have had the infection will be sufficient to prevent the virus from mass spreading,” says Professor Zuzana Bílková of the Faculty of Chemical Technology of the University of Pardubice.
How long will the virus keep spreading in the population?
In my opinion, the virus will keep spreading until there are enough people who have had the disease, or who are fortunate to have an immune system that was able to detect the infection early and eliminate it. When such a number reaches 70-80% of the population, it will not spread as fast. It won’t stop completely, however, until the infection rate reaches 95-98%. Vaccination works on the same principle, by the way.
What principle?
When the vaccination rate in a population reaches 95-98%, even people who have not been or could not be vaccinated are protected. The same model may be translated to the current situation. As soon as there is a vaccine available against the disease, the number of immunized individuals will strongly increase, and thus stop the virus from spreading. The immunological memory that we develop as a result of having an infection or vaccination varies for different infectious agents such as encapsulated bacteria, retroviruses or coronaviruses, but in general prior disease exposure or vaccination protects us against repeated infections. And the SARS-CoV-2 infection is no exception in this respect.
May flu vaccination help to be more immune to the coronavirus?
Absolutely not. The flu vaccines contain only specific antigens that induce the production of specific antibodies and memory cells that respond to the influenza virus only. That is why all the hope is aimed at the new vaccine against SARS-CoV-2 being developed.
What do we currently know about the virus? What makes it special?
In my opinion it is special in how it can spread. As empirical data and first studies suggest, the virus can be spread even by individuals without clinical presentation, i.e. before the disease develops. I believe that there are many people in the community who spread the diseases unknowingly since they show no symptoms. Their immune system can respond fast and effectively, so they never develop the actual disease. That is why it is so important that everyone wears a face mask or a respirator in the public, and thus protects not only themselves, but also the people around them.
What do you think the real number of cases is if not everyone gets tested?
The figures we are getting show the number of people who have been tested positive. In other words, the figures are conditional upon the testing capacity in the respective region and the availability of tests for everyone, i.e. even for those without symptoms. Sometimes we can read in the media that the real numbers of cases (not only those with symptoms) must be ten or hundred times higher. I would even tend to go for the latter. On the other hand, this does not mean a higher lethality or severity of the clinical symptoms.
Will the warmer weather curb the virus?
I do not think that spring and the warmer weather will have a significant impact on how the virus spreads in the population. For the virus to grow, the standard body temperature, i.e. 37°C, is an optimal temperature. All viruses have adapted to such a temperature during their evolution. What is, however, most detrimental to the virus is the drought. When the air humidity decreases and the droplets on surfaces disappear fast, the time of survival of the virus, and thus infectiousness of our environment is reduced. If such surfaces are exposed to direct sunlight, the time of survival also decreases. It is not caused by the UV radiation, but rather by the fact that the droplets dry up faster.
How long can the virus survive?
Irrespective of the environment, the virus particles can survive from 2 to 15-20 hours. That is why personal hygiene and disinfection of surfaces is so important. Combined with airing of enclosed spaces.
Will we be able to live together with the virus after some time?
Yes, the same way as we live with many other pathogenic viruses or bacteria. The difference is, however, that our population does not know the virus and must adapt to it. It is remarkable how universal our immune system is. The population biology shows us that the human immune system can respond to, detect and counteract all infectious agents that have originated throughout the history of human species, and even develops effective immunity against those that may be created artificially in a molecular genetic lab anywhere in the world.
Note, however, that this applies to the population as whole. Thanks to the genetic variability, some individuals have better immunity, whereas others worse, and their condition is more severe, and in some cases even fatal. In addition, elderly patients also suffer from other diseases that may weaken their immune system; these are called comorbidities. We must not also forget that some therapies (e.g. radiotherapy, cytostatic therapy, long-term immunosuppressive therapy following transplantations) also considerably weaken the immune system.
Let me also stress that before the antibiotic and antiviral drugs were developed, the population was subject to natural selection. Individuals whose immunity was weak died in their childhood before reaching the reproductive age, and thus could not transfer this weakness to their children. However, the process of natural selection has not worked now for a number of decades, which makes our population more sensitive to infections.
Some say that children do not contract the disease so fast. Is it possible to confirm or rebut such a theory?
It is not a matter of how fast they contract the disease, but how susceptible they are. Susceptibility means sensitivity to infectious agents. Since a virus is a parasite invading cells, it is released to permissive cells where it is replicated and the particles released from the first cell propagate to other cells. Generally, coronaviruses enter the body through mucosa. The SARS-CoV-2 mostly affects the lower and upper airways. It may, however, also enter the body through eye mucosa or gastrointestinal tract mucosa. For the virus to enter the cells, it must find specific receptors on its surface. Through the receptors, the coronavirus particles attach to the cell membrane and release the content into the cell. Among others, the RNA molecule which carries the genetic information for the creation of virus particles, also enters the cell.
What do the statistics suggest?
The figures describing the ages of the infected patients send us a clear message. It is obvious that the infection affects children much less. Children and young patients usually have mild symptoms.
Do you know why this is the case?
At the moment we do not know why there is such a big difference between the number of infected children and infected adult patients. There may be several explanations. For example, the mucosal epithelium in children does not contain as many specific receptors, and thus it is more difficult for the virus to enter the cell and replicate. Or it may be explained by the fact that the infection rate for various coronaviruses is higher, and thus their immune system can respond to the infection faster and more effectively.
The severity of the disease in patients over the age of 70 is again related to immunity then?
Absolutely. This may be related to the activity of the immune system which deteriorates with age, and the immune system can no longer respond the presence of virus particles so fast. Added to this are the comorbidities which further deteriorate the immune system of such individuals.
What diseases increase the risk and why?
The elderly are at the highest risk. The immune system weakens as we get older. In addition, the elderly often suffer from other diseases which make them more vulnerable. People undergoing radiotherapy or cytostatic therapy also have their immune system weakened. The cancer therapy targets cells that split fast (which is typical of tumorous cells), including the immune system cells that also get killed as part of such therapy. Any infection that people undergoing such therapy suffer may be fatal. Patients who undergo immunosuppressive therapy, i.e. are administered drugs that reduce the efficacy of the immune system on purpose, are also a group at risk. These are usually patients with organ transplants, whose immune systems tries to reject the foreign tissue, and it is thanks to the immunosuppression that the received organ is able to survive in the body. Naturally, such people are more susceptible to infections.
Patients with autoimmune diseases also receive immunosuppression. Auto-immunity describes a situation when the immune system attacks and kills the tissue, such as kidney, lungs, blood cells, of its own body. To prevent such pathological symptoms, the hyper-activity of the immune system must be reduced. The immunosuppressive drugs suppress the immune system as a whole and the patients have worse immunity to the infections.
How can each of us help in addition to having better personal hygiene habits?
The hand hygiene is key, washing your hands regularly and repeatedly, as well as meticulous disinfection of surfaces touched by people’s hands. Such surfaces include shopping trolleys, your wallet, credit card holders, car keys, handles in public transport and public buildings; i.e. all surfaces where we cannot control whether the surface has been contaminated or not.
Therefore, it is recommended to treat all surfaces (e.g. a credit card, wallet, steering wheel, car keys, door handles around you) with alcohol-based disinfectant once you come home from outside.
It is often confusing what we hear about how to wear face masks or respirators and what types to wear. How is it then?
It was a month ago that I wanted to buy face masks at the pharmacy and the pharmacist told me, rather rudely, that there was no point and that they would not protect me anyway. And now they tell us, quite rightly, that where no FFP3 respirator is available, we must make do with lower-category respirators or face masks, even hand-made ones. I cannot agree more. Any mechanical obstacle that prevents the droplets containing the viral particles from spreading in the air and on surfaces is better than staying idle. The virus spreads through droplets that are released when coughing, sneezing or even talking.
Should the face masks be obligatory for anyone?
Face masks should be obligatory both for those who feel signs of the disease and those who feel well. The incubation period in infected individuals takes several days and the spreading of the infection may be considerably reduced by wearing the face mask during such time.
On the contrary, is there anything that we should not exaggerate?
It is as simple as complying with the rules of personal hygiene and not being ashamed of wearing the face mask in the public, even a home-made one, and inviting others to do the same. My family also ridiculed me a few days ago that I was being too strict. Today, when we come home, there are two bottles of disinfection in the hall so that everyone can clean their hands. There is also a stack of face masks so that everyone remembers to wear one when going out.
There is not much more that we can do. We must accept the pandemic as a fact together with all the consequences that it may bring. If we protect ourselves consistently, however, we may reduce the risk for those whose immune system is weaker and are thus susceptible to higher severity of the disease. Solidarity with others is most important.
Is it possible that the sterile environment may be actually damaging to the human body?
Not under the existing circumstances. I can see what you are getting at, the so called the hygiene hypothesis. The immune systems of our children and our generation, who has grown up in an environment with limited presence of pathogens and with better hygiene standards, is less resistant to infections. This is often linked to the higher incidence of pathological responses of the immune system, such as allergies or auto-immune diseases. Their incidence in the population is clearly on the rise and it may be linked to extreme hygiene practices and low exposure of our immune system in childhood and adolescence.
Doctors recommend that we eat foods rich in vitamins and thus enhance our immunity. But can it save us if we start to be more responsible towards our body?
A sudden change in a diet has a limited and only gradual impact, but you can’t go wrong if you start taking vitamin C. There is no overdose risk involved. Naturally, the effect will be enhanced if your diet is diverse and rich in nutrients.
Why is it that most dangerous pathogens come from China?
It is undoubtedly related to the hygienic and dietary habits of the Chinese. Everyday exposure to animal tissue that may be full of viruses that the humans have not adapted to yet may increase the risk of human transmission. There is no herd immunity at the moment and the virus spreads without any limits. As a molecular biologist, I also wonder whether it is mere coincidence that the first COVID-19 case was registered in the Wuhan area when the Wuhan Institute of Virology was opened just some years ago.
Will we cope with the Wuhan virus?
The answer to this questions goes beyond my knowledge of molecular biology and immunology. The question is more related to philosophy and evolutionary biology. But I would dare say that we will. It may involve some human as well as economic costs. On the other hand, this “test” may move us forward and help us realize what is important in life and what is redundant, and thus a sort of “luxury”. It may also change the public’s view of the importance of the healthcare system in the West, the advances of science and the benefits of vaccination with respect to many diseases of which we have lost fear. It is clear that only personal experience and imminent danger can be an eye-opener for many people.
Is there anything comforting that you may say about the spread of the virus?
I believe that Europe will control the virus in two or three months The number of people who have had the infection will be sufficient to prevent the virus from mass spreading. I hope that the clinical trials for remdesivir will be completed by then and the drug will be used to treat patients whose condition is severe. It has already been established that it is safe in humans, which will cut the length of the approval process significantly. A vaccine could be developed within a year.
