Updated April 22, 2020, 11:41 am
Some viruses come and go, some stay for a long time, some forever. The virologist Wolfram Brune from the Heinrich Pette Institute, Leibniz Institute for Experimental Virology, explains in an interview which circumstances make life difficult for a virus and what we can expect from SARS-CoV-2 in this regard.
Mr. Brune, there is a lot of discussion about contact restrictions that are designed to contain the coronavirus and how they are relaxed. Few believe that normality will quickly re-emerge. Some even speak of having to get used to a “new normal”. In your opinion, is it possible that SARS-CoV-2 disappears completely?
Wolfram Brune: It is possible, but you will see how likely it is. The first SARS virus did not reappear in the human population after the outbreak of the 2002/2003 outbreak. SARS-CoV-2, however, has other properties. For example, it is contagious if an infected person has no symptoms yet. So infected people spread it without knowing that they carry the virus. That and the fact that the majority of people have never been in contact with the pathogen probably means that the virus will remain in the population for months or years, possibly forever.
Brune: “SARS-CoV-2 is not human-specific”
Under what circumstances do viruses disappear?
If “disappearance” in the sense of “extermination” is meant, this is actually only possible if the virus does not have an animal reservoir. So if it only occurs in humans, such as smallpox or measles. SARS-Cov-2 is not human-specific. So you have to try to make it at least disappear from the human population. There is one main starting point: herd immunity. It is reached when a certain percentage of the population has become ill or has been vaccinated, i.e. has antibodies against the virus. The percentage depends on how contagious the virus is. There are also viruses that are almost certain to go away – those that cause chronic infection, such as HIV, hepatitis B and C, and herpes viruses.
What role does herd immunity play in a virus like SARS-CoV-2?
SARS-CoV-2 is an RNA virus. With this type of virus you have to assume that it will change. A lifelong immunity is then excluded, the mutated virus can also infect people who have raised antibodies against the original form. If the virus were stable, herd immunity alone would probably be enough to completely stop the infection. As I said, this is probably not the case with SARS-CoV-2. Nevertheless, immunity always has its good side: With related viruses, a new infection is usually not as difficult as the first one.
Are there any examples of viruses that have completely disappeared?
Smallpox is a good example. After a vaccination campaign in the 1970s, they have been considered extinct for many years. The aforementioned SARS epidemic of 2002/2003 and the MERS outbreaks since 2012 could also be ended. Since then, these viruses have no longer been present in the human population. In contrast to smallpox, they are still present in animals. If there were to be another animal-to-human transmission, there could be another epidemic or even a pandemic like we are experiencing right now with SARS-CoV-2.
About the expert: Professor Wolfram Brune is a virologist and head of the “Virus-Host Interaction” department at the Heinrich Pette Institute, Leibniz Institute for Experimental Virology, in Hamburg. He is primarily concerned with the question of how viruses can override a cell’s defense mechanisms and use them as hosts. Her specialty is herpes viruses.
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