A number of reports have brought up the possibility of re-infection with COVID-19. Unlike some other viruses, like chicken pox, that bestow long-term immunity to victims, it appears that COVID-19 does nothing of the sort. It is uncertain, however, whether they are being re-infected by a second exposure or just relapsing after an apparent recovery.
RNA viruses like SARS-CoV2 or Influenza have very high mutation rates. They mutate up to a million times higher than human cells. This happens because RNA is not as good at replicating as DNA. The higher rate of “errors” during reproduction (in other words, mutations), is a result. Sometimes, the mutation does little. Other times, however, it makes the virus more successful at infecting a certain species, faster at replicating, or more toxic. These may be beneficial for the virus, but not for you.
(Note: COVID-19 isn’t the name of the virus; it’s the name of the disease. Scientists named the virus itself SARS-CoV2.)
There is now evidence that SARS-CoV2 is mutating into multiple versions of itself. Eight different strains have been identified, whereas a month ago, there were two.
Most scientists believe the mutated strains aren’t more lethal, just different. This is “comforting” and may help epidemiologists track the origins of an outbreak. The problem is that you may not have immunity to every strain if you recover from being infecting with one.
An example of this is Dengue Fever. There are four or so strains of Dengue. If you recover from one, you are immune to that strain. You aren’t immune, however, from being reinfected with another strain. Due to a phenomenon called Antibody-Dependent Enhancement (ADE), infection with a second strain seems to cause more severe symptoms that are reminiscent of Ebola hemorrhagic fever.
Note: Antibody-dependent enhancement (ADE) occurs when antiviral proteins make it easier for viruses to invade host cells, leading to increased infectivity. This virus uses this to cause a relatively mild viral infection to become life-threatening.
It’s not thought at present that ADE will occur in COVID-19 patients, but scientists are hard-pressed to know for sure why some people that supposedly recovered are getting sick again. Are they infected with a new strain? Are they producing antibodies against it? If so, how long do those antibodies protect the victim from re-infection?
Answers to these questions are scarce, but there is evidence suggesting that individuals do develop antibodies after infection. If so, there should be some immunity conferred, although it may be very temporary.
In the meantime, we can take comfort in the fact that re-infection seems to be a rare occurrence. Hopefully, it will stay that way.
Joe Alton MD
Learn more about infectious diseases caused by viruses in Alton’s Pandemic Preparedness Guide: Dealing with Emerging and Current Viral Threats