It could be your neighbors, or the man who brushed past you at the grocery store. Maybe it’s the last-minute addition to Thanksgiving dinner, or the friend who pulled their mask off next to you at the gym.
Throughout Los Angeles, COVID-19 is closer than ever.
One out of every 145 people in L.A. County is currently infectious with the disease, according to a model released by health officials Wednesday. This is a drastic jump from just two months ago, when the estimate put the rate at about 1 in 880 Angelenos.
“Our situation is getting worse each day,” L.A. County Health Officer Dr. Muntu Davis said at a press briefing Wednesday where the numbers were unveiled.
The county has logged higher-than-ever cases of the coronavirus this week, but the model suggests the true number of people ill is even higher. The county uses a mathematical model to determine how many people — diagnosed or not — are actively contagious with COVID-19 and may spread it to others in the community, based on the number of people ending up in the hospital each day, officials say.
Relying on data through Monday, the county’s data scientists found that approximately 0.69% of county residents, or roughly 69,000 people, can currently transmit the coronavirus to others.
Across the country, other officials calculate similar figures, though the formulas used to reach their estimates often differ. Still, the numbers provide a sense of how health officials are thinking about how widespread COVID-19 is in different parts of the country amid an overwhelming winter surge.
Nationwide, 3.6 million Americans were infectious with COVID-19 as of Sunday, which is about 1 in 100 people, according to a model created by Columbia University epidemiologist Jeffrey Shaman and his team.
Calling the findings a “very high rate of infection,” Shaman warned people to minimize contact with those they don’t live with. “The majority of these contagious individuals are unaware of their infections,” he said in an email to The Times.
In Colorado, officials said this week that 1 in 41 people are currently infectious with COVID-19. In Chicago, officials announced last week that as many 1 in 15 people may have active COVID-19 infections.
The estimates attempt to overcome one of the trickier aspects of this coronavirus: as many as 40% of people infected have no symptoms. And for those who do develop symptoms, studies have found that they are most highly infectious before their cough or headache begins, making it impossible for people to stay safe just by avoiding those who appear ill.
“That’s why winter is going to be dangerous for us, because we want to convince the public who doesn’t have any symptoms to assume you are infected and you can be spreading the virus,” said Ali Mokdad, an epidemiologist at the University of Washington.
With such a high rate of coronavirus spread, bending the curve down becomes more difficult. Once spread begins to accelerate, more people have the virus, so the same activities people have been doing for months become more dangerous. Those activities make more people sick, increasing the prevalence further, and the cycle continues.
“There’s just more COVID milling around our communities,” California’s top health official, Dr. Mark Ghaly, said Tuesday. “You are more likely to get infected with COVID just because it’s more available and more around our communities, even if you behave exactly like you did a month ago.”
Indeed, in L.A. County, health officials have said that the people falling sick with COVID-19 in the past few weeks have not made more trips to stores, restaurants, workplaces or anywhere else than those who fell sick a few months prior. A higher number of people are just falling sick at the same location.
“There’s risk involved even in these seemingly benign interactions,” Davis said Wednesday. “The numbers continue to be alarming.”
The rapid spread has prompted the county to halt outdoor dining and instate a modified stay-at-home order this week. If case numbers do not abate, hospitals could be full in a few weeks and the death count could number in the thousands, officials say.
L.A. County’s estimate comes from its Department of Health Services Predictive Modeling Team, which analyzes COVID hospital numbers each week to determine whether there could be a shortage of hospital beds and ventilators, but also the rate of transmission in the county, known as the R, and trajectory of death counts. The prevalence figure was added in mid-June as a way to try to help people understand the far reach of the virus.
The prevalence is calculated using the number of people being admitted to the hospital each day with COVID-19 in L.A. County. The model assumes that for every one person sick enough to end up in the hospital with the disease, there are 39 others who did not, according to county officials.
Simply put, the number of people recently hospitalized with COVID is multiplied by 40. The data scientists then adjust that figure so that it only includes people who are currently infectious, which they estimate for each person is between 2.5 and 4.5 days.
With so many ill who don’t know it, Thanksgiving could become a dangerous affair, said Department of Health Services Director Dr. Christina Ghaly.
“They’re out there and they’re exposing other people to the virus,” she said. “That family meal is turned into an opportunity for COVID-19 to spread.”
Just because 1 out of every 145 is infectious with COVID does not mean they will necessarily infect others. Encounters with people who are infectious can be minimized by masks, social distancing and limiting the amount of time spent together, particularly in indoor environments.
But the latest estimates include data only through Monday, so rising numbers in the county will likely push the prevalence up further in the coming weeks. That could change if people start acting safer, but it is not guaranteed, Christina Ghaly said.
“We don’t see that happening yet, so I do anticipate that the number will continue to rise,” she said.
