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 鶹ý. "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 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 -- 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.
It was previously acknowledged that many cases resemble simple colds, with infected people treating themselves at home or not at all.
Gabriel Leung, MD, of the University of Hong Kong, sounded an ominous note as to the worldwide implications of these data, if the data hold up.
"We would strongly urge authorities worldwide that preparedness plans and mitigation interventions should be readied for quick deployment, including securing supplies of test reagents, drugs, personal protective equipment, hospital supplies [...] especially in cities with close ties with Wuhan and other major Chinese cities," he said in a statement.
And with these new models, together with reports of asymptomatic transmission, Fischer said that this suggests that in China, this is now a "community-based epidemic, so focusing public health interventions becomes more challenging."
CDC Declares First Quarantine in 50 Years
Taking what it characterized as "proactive and aggressive," but "evidence-based" actions, CDC officials announced on Friday the agency has issued federal quarantine orders for all 195 individuals the U.S. government flew out of Wuhan, which will quarantine them for 14 days.
"We recognize this is an unprecedented action, but we are facing an unprecedented threat," Nancy Messonnier, MD, director of the CDC's National Center for Immunization and Respiratory Diseases, said in a conference call Friday. "This is an aggressive public health response to prevent community spread of this novel virus."
"We are preparing as if this were the next pandemic," she added.
Acknowledging the NEJM report about asymptomatic transmission, Messonnier said that the current diagnostic testing they have right now cannot identify patients in the asymptomatic phase of the illness.
"Screening with a lab test in this setting does not help us identify people who are going on to illness. A negative test won't confirm that people are safe from disease," she said.
CDC officials continue to focus their investigations now on the contacts of the confirmed cases to see if they can determine transmission.
More , and the Trump administration is considering a "mandatory evacuation order" for all U.S. citizens there, according to Politico.
When a reporter asked CDC officials if these quarantine procedures would apply to travelers on commercial airlines from China, the officials said they are "evaluating [the] appropriate strategy, in light of new information." Indeed, Business Insider reported on Friday that Delta, American, and United have
But while these travel restrictions may help to combat U.S. spread of novel coronavirus, Fischer warned in general about the potential for continuing global spread. She noted that the Chinese regional and national government have been able to restrict people's movements, because they are currently on holiday for the Lunar New Year.
However, once that ends, Fischer said these people may be expected to report back to work. For many Chinese, that includes global travel to places with weaker health systems ill equipped to deal with novel coronavirus outbreaks, such as sub-Saharan Africa.
"At the end of the Lunar New Year, when vacation ends, what happens to the Chinese travelers who would normally be traveling for work?" she asked.