Prof Radostina Alexandrova: About 5-6 novel viruses appear every year

Standing within 1.5 metres of an infectious person for 15 minutes is enough for transmission

By no means should we ascribe supernatural properties to this virus. SARS-CoV-2 caused a pandemic because it is a novel virus and people have not built up immunity against it. This novel coronavirus exhibits a relatively low propensity for mutating, two times lower than the regular flu, for example. And yet, there are over 1,000 documented mutations of various degrees of spread, some of them are considerably limited to a specific geographic region, Prof Radostina Alexandrova says in an interview with Monitor.

Prof Alexandrova, to what do you attribute the spike in Covid-19 cases as of late? Is it fair to say that the virus has become more aggressive?

By no means should we ascribe supernatural properties to this virus. SARS-CoV-2 caused a pandemic because it is a novel virus and people have not built up immunity against it, we also do not have a vaccine. At the same time, it is easily transmitted and we are yet to find ways to “counteract” it beyond the normal mitigation measures, which, by definition, cannot be 100% effective. Furthermore, we have entered the cold season, which is conducive to the spread of airborne respiratory viruses, as is the case of SARS-CoV-2. Vacations and the nice summer weather are behind us and now we are spending more time indoors, which is a risk factor considering that close proximity facilitates infection - it is believed that spending 15 minutes within 1.5 metres of someone shedding the virus is enough for it to be contracted. That is what necessitates social distancing and the use of personal protective equipment. I believe that in general we are all keeping good personal hygiene.

Is the virus mutating, though? What are your observations of the trends since the outbreak?

This novel coronavirus exhibits a relatively low propensity for mutating, two times lower than the regular flu, for example. And yet, there are over 1,000 documented mutations of various degrees of spread, some of them are considerably limited to a specific geographic region. Special attention should be paid to a particular mutation (D614G), which formed at the beginning of the year and can now be found in almost every SARS-CoV-2 molecule isolated from a positive sample. At this point, we do not know what that means. Some scientists explain its proliferation with the fact that it originated early enough in the evolution of the virus. Here is the right place to remind that a huge number of the virus mutations are actually “neutral”. This is not a coincidence. The cells of animals and people have not changed massively over the past thousands and millions of years so the viruses have no impetus to be mutating all that much in such a stable environment. That is, unless we push them to mutate in retaliation to our immune response getting boosted by the introduction of specific antiviral agents. But that is a topic for another day. Other researchers believe that the D614G mutation has somehow contributed to an easier person-to-person transmission of the virus. Experts agree that it is in no way indicative of developing more serious symptoms, a longer hospital stay or a higher mortality rate of Covid-19. There is no scientifically confirmed evidence pointing to some of the known mutations or versions of the virus presenting a greater danger to human health.

What should we expect in the winter, with temperatures dropping? Will the circulation of the virus change its pattern?

Viruses thrive in low temperatures. It is believed that cold and dry weather is especially favourable to the spread of SARS-CoV-2. The virus is shed by infected people via respiratory droplets expulsed while breading, talking, singing, sneezing or coughing. Dry weather helps the virus “dry”, which makes it “lighter” and able to hang in the air longer and so travel over greater distances. Cold and dry weather also hampers the immune response of our body - for example, blood retreats from the nasal mucosa, which contains cells and factors of the immune system; micro-sores open the door for the virus. It is no coincidence that both SARS-CoV-1 and SARS-CoV-2 pandemics picked up speed in November 2002 and December 2019, respectively, as these are traditionally the coldest months in China. In addition, those two years turned out to be the driest ones too.

Do you think it was a mistake for children to start the new school year back in the classrooms? Have schools become hotspots?

We were all hopeful and eager for the school year to start with in-person attendance. The observations of the European Centre for Disease Prevention and Control (ECDC) show that the reopening of schools in the EU in the spring of this year did not lead to a considerable jump in the infections rate across society. Denmark has the best record in that regard. On the other hand, Israel's experience from May 2020 revealed that, in the absence of safety measures, schools can turn into dangerous coronavirus hotspots. We need to take into account the specific realities and respond in the best way possible. There are no foolproof recipes and easy solutions.

A British study shows that in the case of asymptomatic patients, the count of antibodies drops faster. Is such a conclusion well founded?

The immune response against SARS-CoV-2 continues to be a puzzle with a number of missing pieces. Experts have detected antibodies at least four months after the patient contracted SARS-CoV-2 and are working hard on examining the cellular immune response. There are reports of a direct correlation between the severity of the Covid-19 disease and the longevity of the immune response built up against the virus. But we have more questions than answers at this point. We have no idea how long people who have battled this virus stay immune to it, we do not know what count of antibodies is enough to protect that person from a second infection and whether it will stop the infection altogether or just mitigate the severity of the disease. It has been established that reinfections with coronaviruses, which result in regular colds, are not rare and start about the sixth month after the initial infection, while the maximum lag is one year. It remains to be seen how that plays out in the case of SARS-CoV-2.

Many doctors expect lower rate of infections with the regular flu this year because of the mitigation measures introduced. Can we trust this forecast, considering that there was once again shortage of flu shots?

Experts say that the flu season in the Southern Hemisphere, which just ended, was relatively calm. The World Health Organisation also said that the circulation of flu strains is comparatively low for this time of the year. That positive development is owing to the strict mitigation measures introduced to battle Covid-19. The reason is that SARS-CoV-2 and the flu are spread the same way. This year, it is especially important that we protect ourselves from the flu. This way, we would not only be sparing ourselves the inconvenience and suffering, but avoid burdening the healthcare system. The knowledge collected in the early 2020 shows that one can simultaneously have the flu and the novel coronavirus. Hospital data from China and the US point to that. It is unclear how likely that is to happen. Experts do not reject the possibility of the two viruses helping each other - in suppressing the immune response of the infected person.

Is it reasonable to believe that the flu shot can build a better immunity and somewhat protect us from Covid-19?

The flu shot is designed to create immunity against a particular strain. According to a study of over 13,000 people (both vaccinated and non-vaccinated in preparation for the 2019-2020 season ), the flu shot had not pushed up Covid-19 infection rates or the severity of the disease. That is on one hand. On the other hand, there are, not official as of yet, reports that among people over 65 who were given flu shots in the US and Brazil - two of the countries hit hardest by the pandemic worldwide - the Covid-19 rate of infections was lower, as was the percentage of people hospitalised and of deaths. In general, though, the authors assume that could be due to the flu vaccine's ability to affect general cellular and molecule mechanisms of the immune system. It is too early to make such a conclusion as testing such a hypothesis requires purposeful, in-depth studies.

Is there a study telling us at what intervals such pandemics occur? Is there a cyclical element to them?

Every year, about 5-6 viruses previously unknown to us appear. Fortunately, it is very rare that one of them is simultaneously pathogenic in people and can be transmitted by air. Pandemics caused by flu strains come every 10 to 40 years, with the last one being the 2009 swine flu, prior to which were the 1968 Hong Kong virus and the 1957 Asian flu. Since the turn of the century, there have been three new coronaviruses pathogenic for people, the third one being Covid-19. There is no way to tell whether and when another such coronavirus (or another virus) will appear. But our harrowing experience with the current pandemic shows that serious funds need to be invested in medicine and scientific research. We should try to study what happens inside bats, who are potential incubators for novel viruses; whether there are viruses that knock on our door. We should prepare for them, study the factors that contribute to the emergence of hotspots and their transformation into epidemics and pandemics. We should change our attitude towards nature.


Prof Radostina Alexandrova is an alumnus of the Biological Faculty of Sofia University “St Kliment Ohridski”. She has a PhD in virology and teaches morphology at the Bulgarian Academy of Sciences' (BAS) Institute for Experimental Morphology, Pathology and Anthropology with Museum. She is a part-time lecturer at the Biological Faculty and the Medicine Faculty of Sofia University “St Kliment Ohridski” and at the BAS' Post-Graduate School. She has authored and co-authored more than 180 scientific articles published in national and international magazines as well as congressional and conference digests. She is a member of the Union of Scientists in Bulgaria and is part of the management team of the Immunology Association of Bulgaria.

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