HMM: Far-Reaching Effects of Asymptomatic Coronavirus Transmission.
With asymptomatic transmission of novel coronavirus confirmed outside China, plans to identify the virus by current screening measures may not be enough.
“This underlines that … trying to keep out people symptomatic with respiratory disease is not a guaranteed approach,” Julie Fischer, PhD, of Georgetown University in Washington D.C., told MedPage Today. “Screening for symptomatic people has limited utility in many settings, and it should not be the primary strategy in trying to prevent disease across borders.”
The CDC recently increased its airport screening measures for travelers returning from China, expanding them to 20 U.S. airports.
Fischer cited the reproductive number of around 2 recently reported in The New England Journal of Medicine, saying that based on that number, the virus appears to have a relatively high transmission rate.
“If we assume that transmission is ongoing [there are] going to be many more imported cases and there will be local human-to-human transmission,” she said, adding that this is not the same thing as community-wide transmission.
Fischer said that one of the main questions remains whether we can take action to prevent this virus from spreading outside China, noting that we could see a “shift in strategies in the U.S. and other countries from preventing imported disease to trying to recognize transmission where it happens.”
The outbreak in China continues to rage, with the latest data indicating a total of 9,776 global cases, and 213 deaths, all in China. CDC officials on Friday said the number of cases in China has jumped 26% since Thursday, with over 7,000 cases reported in the last week.
But data published in The Lancet on Friday suggested the real total is much higher — around 76,000 cases in the city of Wuhan alone. The researchers also estimated a higher basic reproductive number of around 2.7.
Fischer noted that confirmed cases are likely only those with severe enough disease to be reported in the formal healthcare system.
“The models are based on best available data [and they] may be trying to point to the iceberg below of asymptomatic disease or mild disease … that would be hard to pick up by health systems,” she said.
On the one hand, it’s good that most cases seem to be mild. On the other hand, it means much more transmission by people who feel well enough to be out and about, instead of sick enough to stay home.