Epidemiologists say the actual number of infections is likely much higher than the official numbers. Even with testing more widespread than during the first few months of the pandemic, many people who have never had symptoms may not have been tested or counted.
Ira Longini, professor of biostatistics at the University of Florida, estimates that around 20 percent of Americans had the virus – more than twice as many as reported. Statistical modeling he recently did for Florida suggests that a third of the state’s population will be infected at some point, quadrupling the reported percentage.
It would need a coordinated nationwide Study to go beyond modeling estimates and have a solid understanding of how many people actually had the virus, he said. The CDC does some serological testing, he said, but not enough to give a complete picture.
“The end result is we don’t know, but we can guess from the modeling,” said Dr. Longini.
The proportion can vary greatly from place to place. Almost one in four residents tested positive in Dewey County, SD, compared to one in 200 in San Juan County, Washington.
Many of the American metropolitan areas with the highest number of cases reported relative to their population are in the south or southwest, where the virus has spread rapidly lately, but some are in areas like the Great Plains, which got worse in the fall. The top 5 are Yuma, Ariz .; Gallup, NM; Bismarck, ND; and Lubbock and Eagle Pass, Texas.
The metropolitan areas with the most new cases per capita in the past two weeks reflect the same trend, and also highlight the virulence of the California outbreak. These areas are Laredo and Eagle Pass, Texas; Inland Empire, California; Jefferson, Ga .; and Oxnard, Calif.
More than a million people are known to have tested positive in Los Angeles County, one of the country’s hot spots in recent months. And George Rutherford, professor of epidemiology and biostatistics at the University of California at San Francisco, estimated that the actual number of infections there is twice as high as one in five Angelenos.
“It’s not enough for herd immunity, but it’s enough to blunt the curve,” he said.
