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Updated on April 22, 2020 at 11:41 a.m.
Some viruses come and go, some remain long, others forever. Virologist Wolfram Brune of the Heinrich Pette Institute, Leibniz Institute of Experimental Virology, explains in an interview what 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 relax. Few believe that normality will quickly re-emerge. Some even talk about having to get used to a “new normal”. In your opinion, is it possible that SARS-CoV-2 disappears entirely?
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 still has no symptoms. Then infected people transmit it without knowing that they carry the virus. That and the fact that most 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 you mean “disappearance” in the sense of “extermination,” this is actually only possible if the virus does not have an animal reservoir. So if it only occurs in humans, like smallpox or measles. SARS-Cov-2 is not specific to humans. Therefore, you must try to make it at least disappear from the human population. There is a main starting point: collective immunity. It is reached when a certain percentage of the population has become ill or has been vaccinated, that is, they have 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 must assume that it will change. Then a lifetime immunity is excluded, the mutated virus can also infect people who have high antibodies against the original form. If the virus were stable, the collective immunity would only be enough to completely stop the infection. As I said, this is probably not the case with SARS-CoV-2. However, immunity always has its good side: with related viruses, a new infection is generally 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 MERS outbreaks since 2012 could also end. Since then, these viruses have no longer been present in the human population. Unlike smallpox, they are still present in animals. If there were another animal-to-human transmission, there could be another epidemic or even a pandemic like the one we are currently experiencing 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, Hamburg. It is primarily concerned with the question of how viruses can defeat a cell’s defense mechanisms and use them as hosts. Her specialty is herpes viruses.
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