As the pandemic wears on, more people are claiming the virus has infected them twice. Experts are now trying to determine whether these reports are indeed legitimate reinfections or long-term effects of the disease.
The Centers for Disease Control and Prevention states they are investigating claims of reinfection, but only those that occur more than 90 days apart.
According to USA Today, several states have reported cases of reinfection including 120 in Washington state. Health experts say these occurrences are rare and must be proven by genetic testing to ensure slightly different viruses caused the reinfection, and so far, only a handful have been confirmed.
A case study published in The Lancet revealed a 25-year-old man in Washoe County, Nevada, suffered two episodes of COVID-19, one in April and the second at the beginning of June. Genetic testing showed the viruses that caused his two bouts with COVID-19 were different, so it was not a case of one prolonged illness. In fact, the second time around he had a worse outcome from the disease.
Researchers said, while infection with SARS-CoV-2, the virus that causes COVID-19, does elicit an immune response, we do not know why some people are still susceptible to infection.
According to Mic, our lack of knowledge about the novel coronavirus makes it difficult to predict how the human immune system will respond, even if antibodies are present to combat the disease. The Nevada incident was not isolated as another distinct case of reinfection was noted in South America. That person was also reportedly sicker the second time around.
''Our understanding of the immune response is that the majority of people who are infected mount an immune response within a few weeks of infection,'' said a spokesman for the World Health Organization, according to USA Today. ''We are still learning about how long the antibodies last. So far, we have data that shows the immune response lasts for several months.''
Antibodies that provide protection against COVID-19 may be viable for months after infection, according to new research from Iceland. Scientists measured the levels of SARS-CoV-2 antibodies in the blood of approximately 30,000 study participants, including 1,200 who tested positive for the virus and recovered. They found 91.1% of those who had recovered from COVID-19 had antibodies against the virus months after infection. Their results were published in The New England Journal of Medicine.
According to Nature, those protective antibodies actually rose during two months after diagnosis and remained at high levels for an extended period of time.
''Our results indicate that antiviral antibodies against SARs-CoV-2 did not decline within 4 months of diagnosis,'' wrote the authors.
However, if reinfection is possible, then experts say this will have a dramatic effect on achieving herd immunity, even with a vaccine to contain the spread of the virus.
People might get antibodies to the virus and then lose them, said Dr. Jeffrey Shaman, a professor in Environmental Health Sciences at Columbia University Mailman School of Public Health, who is investigating the possibility of reinfections. He cited the 1918 flu that came back repeatedly, but lost some of its impact because people eventually developed some resistance to the virus, according to USA Today. Hopefully, a vaccine will have a similar effect and help people build up a tolerance to COVID-19.
But until scientists have more answers, Shaman suggests people who have been infected continue to wear masks and observe social distancing.
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