Millions of US residents have been infected by the virus that causes covid-19, and at least 160,000 are dead. One effect is that the pool of susceptible individuals has been depleted in many areas. After infection, it’s believed, people become immune (at least for months), so they don’t transmit the virus to others. This slows the pandemic down.
“I believe the substantial epidemics in Arizona, Florida and Texas will leave enough immunity to assist in keeping COVID-19 controlled,” Trevor Bedford, a pandemic analyst at the University of Washington, said on [August 7], in a series of tweets. “However, this level of immunity is not compatible with a full return to societal behavior as existed before the pandemic.”
The exact extent to which acquired immunity is slowing the rate of transmission is unknown, but major questions like school reopening and air travel may eventually hinge on the answer.
What is known is that after rising at an alarming pace starting in May, new cases of covid-19 in Sun Belt states like Florida have started to fall.
“Immunity may play a significant part in the regions that are declining,” says [computer scientist Youyang] Gu. At least until the fall, which is how far his models look forward, he says, “I don’t think there is going to be another spike” of infections in southern states.