4 surprising reasons scientists think asymptomatic cases of coronavirus are so common


The coronavirus is a serious, often fatal pathogen, but the Centers for Disease Control and Prevention estimates 40 percent of all cases are asymptomatic. In some isolated outbreaks in prisons and food processing plants where thousands of people administered COVID-19, up to 94 percent of infected individuals presented no symptoms. The Washington Post spoke with experts and suggested four possible reasons why, although it is important to note that the research is in early stages in all cases.

T-cells: T cells, a type of white blood cell that generally provide longer-lasting immunity than antibodies, can be the key to understanding resistance. One research group found that, among uninfected blood samples donated to a blood bank between 2015 and 2018, a “remarkable” 40 to 60 percent recognized the coronavirus, suggesting that some people may have an immune response based on memory of others, less potent coronaviruses.

Fax: The Mayo Clinic is studying whether vaccines for other pathogens can protect against the virus, as has been proven in other situations. Seven types of vaccines received one, two, or five years in the past were found to be associated with a lower rate of coronavirus infection, particularly pneumonia and polio vaccines.

Allergies: Scientists have noted that children with asthma and allergies are surprisingly not at high risk of developing serious cases of COVID-19. One theory is that these children have a reduced number of ACE2 receptors, the protein that the virus attaches to before it replicates in the body. Without these receptors, the virus’ chances of reducing damage would decrease, which means that allergies can provide protection in this case.

Masks: Masks are discussed as a preventative measure, but they can also contribute to more mild infections. The most direct proof of this theory is a comparison of two cruise ships. On the Diamond Princess, where masks were not used, 47 percent of the positive cases were asymptomatic, while an Antarctic-bound Argentine cruise ship that had a similar outbreak but provided masks to all passengers and crew, saw an 81 percent asymptomatic rate. Read more at The Washington Post.

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