Casanova and his colleagues have previously found genetic mutations that increase a person’s susceptibility to infectious diseases, such as severe pneumonia caused by influenza.
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“There are many, many infectious diseases for which genetic variations have been shown to be causal,” Casanova said. “So when covid occurred, if I may say, it’s business as usual.”
How the virus infects you — and how much
Numerous papers have explored whether different strains of the virus are more transmissible or lethal. One strain has become dominant in much of Europe and the United States. That strain has a genetic mutation affecting what is called the spike protein — the structure that lets the virus bind to receptor cells in humans.
So far, there is no consensus that this or other mutations are significant from a clinical standpoint. Collins, the NIH director, says of the different strains, “I think they’re all acting the same.”
Another possibility frequently discussed by researchers is that the mode of transmission is key to understanding the severity of the disease. Many scientists argue that, contrary to what the World Health Organization and the Centers for Disease Control and Prevention have repeatedly stated, the virus sometimes spreads through tiny aerosol particles, not simply through large respiratory droplets.