Ochsner Study Finds 75% of People With COVID-19 Have No Symptoms

Jul 2, 2020

A strikingly high number of people who have the coronavirus and are infectious also have zero symptoms, according to a new Ochsner Health study.

In a snapshot of the virus’s spread conducted in the metro New Orleans area in early May, 75 percent of people in the early stages of the virus — the period when they’re most infectious — were asymptomatic; 40 percent who had had the virus at some point never showed symptoms over the course of their infection.

“I ran the analysis a couple of times, because I just could not believe those numbers,” said Amy Feehan, the study’s principal investigator and a research scientist at Ochsner Health.

The results come from an Ochsner Health COVID-19 prevalence study released today. Researchers drew from a volunteer pool of roughly 25,000 people to select a representative sample of the populations of Orleans and Jefferson Parish. They then tested the selected 2,640 participants using both a COVID-19 and an antibody test from May 11 through May 15.

The results come amid a second week of rising cases and hospitalizations across Louisiana and a rising percentage of positive test results, despite the state’s ongoing effort to test more people.

In response to worrying trends in Baton Rouge this week, Mayor Sharon Weston Broome announced mandatory face coverings in public, and federal and state officials launched new sites to boost testing in the city by 5,000 tests a day.

The study also comes as Ochsner Health announced it would be restricting COVID-19 tests at its hospitals and emergency rooms to only those with symptoms — a response to a shortage of testing supplies amid rising demand.

Overall, the study found that 7.8 percent of Jefferson and Orleans Parish residents had had the virus at some point by mid-May. It found a fatality rate of 1.63 percent that was relatively stable across different races — the exception being that Asians had a fatality rate of just 0.61 percent. But the prevalence of the virus was much higher in Black communities — particularly New Orleans East.

While that death rate is lower than what the state has found for cases it’s collected, Feehan noted that figure is 10 to 40 times more deadly than the flu.

The study also found that symptoms did not increase or decrease the amount of virus or antibody response. And contrary to current concerns of the rising number of cases among younger people, the study found that older people — those 60 to 79 years old — were more likely to be asymptomatic.