Covid-19 Transmission Rate In Los Angeles Creeps Up In Recent Weeks

“The R has been creeping up steadily now for the past 3 weeks,” said Dr. Christina Ghaly, the Director of the Department of Health Services for Los Angeles County on Monday. That rate is the calculated rate of Covid-19 transmission in the county.

County Public Health Director Barbara Ferrer reported in a Zoom meeting with reporters that the estimated transmission number was 0.93 in early March, up from 0.87 the week before. The range of uncertainty is from .085 to 1.04. Any R number over 1 means that every person infected is passing the virus on to more than one other county resident. In a region of 10 million, infections can quickly snowball.

According to an L.A. County report issued Monday, the rate of decrease in patients at local hospitals has also begun slowing. The report says that, because of the range of uncertainty in the R number, it is currently unclear if “the number of hospitalizations will continue to decrease, remain stable, or increase.”

For comparison, in early November R went from 0.95 to 1.02 in a week. We all know what happened shortly thereafter. But March 2021 is very different from November 2020.

While the R has been rising, Ghaly said that “the base on which the R acts is incredibly important. The lower base of cases that we’re operating on now is incredibly important.”

Indeed, officials reported just 516 new cases and nine additional fatalities on Monday, though those relatively low numbers may reflect reporting delays from the weekend. In early November, the county was reporting about 1,800 new daily cases and 22 additional deaths. So the daily totals are far, far below where they were even a month ago, meaning a rise in transmission would not have the same impact it once would have.

“I don’t think we’ll EVER get back to the disaster we saw in spring and early summer,” said the usually cautious Ferrer. “There are a large number of people [now] vaccinated. We’re nowhere near herd immunity,” she continued, “but there is a lot of protection. In our skilled nursing facilities, we will not see a surge like we saw in June.” Ferrer said the same goes for heath care workers, many of whom are now inoculated.

Ferrer urged caution, even as she announced broader reopening for bars and breweries. She noted that Miami, which is seeing Spring Break crowds, has a 9% test positivity rate. L.A.’s number, according to the county dash board, is 1.70%.

“When you see that, in one week, that cases soared in places like Michigan…to 3,000 in one week,” Ferrer said she does not want to see a spike like that in L.A.

Asked whether increased public activity or more infectious variants may be to blame for the data, Ghaly speculated that it is likely a combination of the two.

“Just based on the timing, it’s not based on the reopening,” she said. “That’s just not consistent. The model notices the slowing in the rate of hospitalizations. It might not be the variants and could be behavior, but more likely a combination of the two.”