Jan 27, 2020 - Science

Americans still have low risk of coronavirus infection, CDC says

CDC official holding a press conference.

National Center for Immunization and Respiratory Diseases Director Nancy Messonnier speaks during a press conference on the coordinated response to the coronavirus outbreak. Photo: Samuel Corum/Getty Images

The risk of U.S. residents becoming infected by the coronavirus that's devastating China remains low right now, public health officials said Monday, even as there's growing pressure to ramp up U.S. and international pandemic preparedness.

The latest: There are at least 2,886 confirmed cases of 2019-nCoV in 16 countries or regions and 82 deaths in China. The U.S. has five confirmed cases with 110 people in 26 states under investigation so far, 32 of whom tested negative, according to the Centers for Disease Control and Prevention.

"At this time in the U.S., the virus is not spreading in the community ... the risk remains low."
— Nancy Messonnier, director of the CDC's National Center for Immunization and Respiratory Diseases, at a press briefing

Reality check: At the moment, the influenza outbreak is more dangerous to Americans. The CDC says flu activity remains high — this season so far has an estimated 15 million illnesses, 140,000 hospitalizations and 8,200 deaths (including 54 children) in the U.S. as of Jan. 18.

"Absolutely, the flu is a bigger risk for Americans than the coronavirus, right now."
— Melissa Nolan, an infectious disease expert, tells Axios

Yes, but: Because this is a new coronavirus, and there are many "unknowns" about it, there's the potential for a pandemic, which the CDC acknowledged on Sunday.

  • And, if the Chinese health ministry is correct when they say people begin shedding the virus before showing symptoms, this could be a game-changer.
  • "This would be very unusual, and very concerning," as a similar coronavirus, SARS, was not contagious before symptoms appeared, Nolan says.
  • But, Messonnier says they have not seen this in the U.S., where so far all confirmed cases have been people who've traveled in Wuhan.

What's happening now: The U.S. will continue screening passengers coming indirectly from Wuhan at five airports, conduct contact tracing for all confirmed patients to monitor for new infections, and publicize research via GenBank so labs can develop targeted diagnostics, treatments and vaccines.

What we know so far: It's early days in investigating this virus, so some reports may be based on too few samples or show an incomplete picture.

  • It "doesn't look like the virus has mutated" yet, at least when the U.S. compares the genetic sequences of China's initial sequencing of the virus and the first two American cases, Messonnier says. If it continues to mutate slowly, diagnostics, treatments and vaccines are likely to be more effective.
  • The incubation period appears to be around 2–14 days, she adds.

What we don't know: Per Nolan, who is an assistant professor at the University of South Carolina’s School of Public Health, researchers need to determine...

  • What is the animal "reservoir" where the virus first transmitted to humans, so it can be culled.
  • How contagious is this virus — such as looking at how fast it "reproduces," called R-naught. One initial report says the average infection rate is about 2.6 people per infected person — this is higher than SARS' rate of 2.0 but less contagious than measles, which is around 12-18. "In general, you want the R-naught to be below one," Messonnier says.
  • Whether super-spreaders, or people who shed the virus more than most, are transmitting the virus to others. Reports point to the possibility that one person infected 15 health workers in China.

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