Two travel-associated cases of novel coronavirus were confirmed in California, along with another in Arizona, bringing the total to five confirmed travel-associated cases in the U.S., CDC officials said on Sunday.
Similar to the previous two cases, the infections were in patients with recent travel to Wuhan, China. All five patients remain hospitalized, where they are being evaluated on a "case-by-case basis." CDC and state health officials continue to investigate these patients' contacts, and putting them in tiers based on risk.
On a conference call Sunday, a reporter asked CDC officials about reports that the virus can spread during the incubation period and that it has become better at spreading among humans.
"We at CDC don't have any evidence of patients being infectious prior to symptom onset," said Nancy Messonnier, MD, CDC director, National Center for Immunization and Respiratory Diseases.
She noted that, since the CDC last held a briefing on Friday, the cumulative number of U.S. patients under investigation jumped from 63 to more than 100, with more expected in the coming days. Of these, 25 have tested negative along with the five whose infections were confirmed. The agency said that it plans to update numbers on its website on Mondays, Wednesdays and Fridays.
"We are getting calls all day, all night from clinicians," Messonnier said, adding that CDC welcomed the outreach. "We want clinicians to call if they have a patient they are concerned about."
The New York Post reported that a retired Wuhan with novel coronavirus. (Later reports, however, cast doubt on whether had treated patients.)
Messonnier urged clinicians to both be on the lookout for patients returning from Wuhan with fever or respiratory symptoms, but also to "take care of yourself and follow recommended infection control procedures."
Over the weekend, coronavirus case counts in China surged dramatically -- from under 900 on Friday to , according to Reuters. Deaths from the novel coronavirus have risen from 26 to 81 in the span of a few days. As of Sunday, 14 countries worldwide have confirmed cases. Many have instituted or are considering restrictions on travelers from the affected areas in China, and/or evacuation of their own citizens.
CDC officials confirmed media reports that the State Department is planning "safe and expedient departure of [U.S.] citizens in China," and that CDC is involved in the coordination and planning of these efforts.
On Saturday, the New York Times Twitter account displayed a video that seems to depict , including patients crowding the hallways and pleading, "Save my life, doctor!"
"Some of the reporting out of Wuhan is alarming," Messonnier said, adding that at the risk to the U.S. remains low. "At this time, novel coronavirus is not spreading within our community."
But questions remain about exactly how infectious the virus is. A report by researchers at the Imperial College London (ICL) on Saturday concluded that "self-sustaining human-to-human transmission of the novel coronavirus ... is the only plausible explanation of the scale of the outbreak in Wuhan."
The ICL group estimated the , or the number of secondary cases produced by a single infection in a susceptible population, is 2.6, while ranged from 2-5, noted The BMJ on Friday. These estimates differ from the World Health Organization which put the virus' basic reproduction number at a range of 1.4 to 2.5.
Messonnier said the CDC posted the entire viral genetic sequence from the first U.S. patient on Friday. Researchers are also continuing to grow the virus in their labs, and will share that information once it becomes available.
She emphasized the importance of "precision" and caution, and pointed out that the U.S. has faced multiple pandemics of varying degrees and severity.
"We need to be preparing as if this is a pandemic, but I hope not," Messonnier said.