An estimated 320,000 adults in Los Angeles County may have been infected with a coronavirus, according to preliminary results of a study that suggests the disease is much more common than current tests show, and that the death rate is much lower.
The county and University of Southern California study from April 10 to 11 estimated that approximately 4.1% of the county’s 8 million adult population had antibodies to the virus. When adjusted for the margin of error, the infection rate ranged from 2.8% to 5.6%, or approximately 220,000 to 440,000 adults.
The study, which has been criticized by some outside experts, follows on from other research that suggested that more people had had a coronavirus than previously determined through tests – many without symptoms or without feeling sick enough to request a test. But it also means that more people are silent carriers of the virus that has killed more than 1,200 people in California.
Public health officials have stressed that the results do not mean that people should stop practicing social distancing and assume that most people are still susceptible to the virus.
“Given the high rate of people who may have been infected with COVID-19 at any given time, we must assume that at any time we could be infected and that everyone else we come into contact with could also be infected, “said Barbara Ferrer, director of public health.
The study was similar to that of 3,300 residents of Santa Clara County in early April, which estimated that 48,000 and 81,000 of the 1.9 million people in the county – between 2.5% and 4.2% – had been infected.
The Santa Clara study, which used some of the same researchers as the USC, was heavily criticized for its methodology, which recruited volunteers on social media. The test he used – the same one used by the USC – has been criticized as unreliable for producing false negative or positive results.
Dr. Eric Topol, professor of molecular medicine at Scripps Research, said the tests were not well validated and overestimated the number of people infected. Some may conclude that if many people have been infected without symptoms severe enough to request a test or medical attention, this is not a major threat.
“The problem is that they gave a false feeling that it is not a bad virus after all,” said Topol. “These are bad calculations, bad tests, and bad results for the confusion it causes. “
Unlike the Santa Clara study, the USC used subjects representative of the county population that were part of a database of market research companies. Neither study was peer reviewed, a critical step in the publication.
Dr. George Rutherford, an epidemiologist at the University of California at San Francisco, said that many research results on coronaviruses are published prematurely. While he doesn’t think the results will affect decisions to let people go back to work, they could be problematic.
“This is the time when ultra-critical decisions are made,” said Rutherford. “It could be summed up as something that someone hangs their hat on and it turns out that it is not peer reviewed … and excited … and you come to the wrong conclusion. “
Until the results of the study were announced, Los Angeles relied on testing people who were sick or had symptoms of the virus to determine the rate of infection. But this statistic is biased because only a limited number of people can take the test and many people would be asymptomatic or may have symptoms consistent with the flu or colds that also prevail at this time of the year.
At the time of the test, the county had reported almost 8,000 cases, which means that the actual number was probably 28 to 55 times higher and that the death rate was much lower than that based on the number of people tested.
“The death rate is not the only number we should focus on,” said Neeraj Sood, professor of public policy at USC. “What the results show is that only 4% of our population has been infected, which means that we are very early in the epidemic and that many more people in LA County could potentially be infected. And as this number of infections increases, so do the number of deaths, the number of hospitalizations and the number of ICU admissions. “
On Monday, the county had 13,816 cases out of 80,000 tested, or 13% positive, the county said. The county has killed more than 600 people, which is about half of the state’s total. The county has 10 million residents, a quarter of the state’s population.
Testing has been problematic around the world with a shortage of supplies to collect and transport samples and not enough protective clothing for the people administering the test. Governor Gavin Newsom and US officials have said that more robust testing and the ability to track people who may have been infected with each person tested positive is essential to lift restrictions on leaving home.
Authorities are also trying to gain a better understanding of how widespread the virus is among the homeless.
Los Angeles began sending medical teams to the streets on Monday to provide homeless people with medical tests and rapid virus tests.
A line has meandered into the block at a new pop-up test clinic on Skid Row which is staffed by the Los Angeles Fire Department. Those infected will be offered transport to makeshift shelters or hotels where they can be treated while remaining isolated.
At least 47 homeless people tested positive for COVID-19 in Los Angeles County, health officials said. A dozen of them were not sheltered. Investigations are underway at eight homeless shelters to determine whether staff or residents should be quarantined.
California recorded more than 33,000 cases on Monday and 1,225 deaths, according to a count from Johns Hopkins University.
For most people, the coronavirus causes mild or moderate symptoms, such as fever and cough, which go away within two to three weeks. For some, especially the elderly and people with health problems, it can cause more serious illnesses, including pneumonia and death. The vast majority of people recover.