Cases spike in Wuhan mystery pneumonia cluster

The number of patients infected in an unexplained pneumonia cluster in the Chinese city Wuhan jumped from 27 to 44, with questions swirling around not only about what pathogen is sickening people, but also how patients were exposed.

Wuhan's health department said in an update today that of the 44 patients, 11 have severe infections, and 121 close contacts are under observations, according to an official statement translated and posted by FluTrackers, an infectious disease news message board.

Tests rule out routine respiratory viruses

Some of the people sickened in the outbreak operated stalls at the same seafood market, which reportedly sold birds, pheasants, snakes, and the organs of rabbits and other animals, and so far there is no evidence of human-to-human spread or infections in healthcare workers. Wuhan officials said the illness appears to be a viral pneumonia, but tests have ruled out common causes such as flu, avian flu, and adenovirus.

Experts in and outside of China have raised the possibility that a new type of coronavirus may be the culprit. Coronaviruses can trigger a wide range of respiratory symptoms with some types causing mild cold symptoms, with others such as the severe acute respiratory syndrome (SARS) virus or Middle East respiratory syndrome coronavirus (MERS-CoV) known to cause severe or fatal infections.

Local health officials are continuing the investigation, which includes looking for more cases, and have cleaned and sanitized the seafood market, which was ordered closed yesterday.

Screening flags more Hong Kong travelers

Some Asian countries have stepped up screening in travelers arriving from Wuhan, and Hong Kong has identified two more sick travelers, but so far, there is no indication that their illnesses are linked to Wuhan's pneumonia cluster.

Hong Kong's Center for Health Protection (CHP) in its latest update said the two latest sick travelers were females ages 12 and 41 who are in stable condition and are being treated in isolation. They had visited Wuhan in the last 14 days, but neither had visited a live animal market before their symptoms began.

Of five travelers flagged in Hong Kong's screening, two have been discharged. A separate CHP report on the patients' statuses said three of the five tested positive for flu, all the H3N2 subtype.

In a related development today, the CHP revised its reporting criteria to widen its surveillance for possible cases. It asked doctors to report any patients who have fever with respiratory illness and pneumonia who have traveled to Wuhan within 14 days of symptom onset, even if they did not visit any of the city's live markets or seafood markets.

Critical questions about case definition

Michael T. Osterholm, PhD, MPH, director of the Center for Infectious Disease Research and Policy (CIDRAP), which publishes CIDRAP News, said it's too early to say if the Wuhan cluster marks a significant public health emergency.

Aside from identifying the unknown pathogen, another piece of the puzzle is the case definition Wuhan officials are using identify patients that are part of the cluster. "This key fact add substantial meaning and context to the case numbers they're reporting," he said.

For example, it's not clear if health officials are excluding sick people who weren't exposed to the seafood market. Osterholm said if they are, the concern is that they could be missing cases outside of the market setting, some of which might reflect human-to-human spread. Presumably, some of the contacts under monitoring are healthcare workers, he added.

The latest official reports suggest some of the patients were working at the market, but it's not clear if others had different epidemiological links or no direct links.

"This is a fluid situation," Osterholm said.

See also:

FluTrackers thread

Jan 3 CHP statement

Jan 3 CHP surveillance update

Jan 3 CHP letter to doctors

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