The vast majority of human H7N9 cases in China have been described as solitary, sporadic infections and usually linked to live bird exposure. Only rarely have contacts of known cases tested positive for the virus.
Last month we did look at a couple of nosocomial infections, including EID Journal: Nosocomial Co-Transmission Of H7N9 & H1N1pdm09 which involved 2 patients at a hospital in Zhejiang Province in 2014, and in NEJM: Probable Hospital Cluster of H7N9 - China, 2015, a cluster involving a patient and two doctors, again in Zhejiang Province.
As far back as the first outbreak in the spring of 2013 we’ve seen signs of limited H-2-H transmission of the H7N9 virus (see BMJ: `Probable Person-to-Person Transmission’ Of H7N9), although they remain pretty rare.
Two weeks ago we looked at the batch reporting of H7N9 cases from January and February, but they contained little or no detail. Today the World Health Organization posted the official notification, and note that among the 29 cases, there were three family clusters.
Whether this is a sign of better transmissibility, a matter of chance, or simply the result of better investigation and reporting, is hard to know. It is, however, something to keep an eye on in future reports.
On 18 March 2016, the National Health and Family Planning Commission (NHFPC) of China notified WHO of 29 additional laboratory-confirmed cases of human infection with avian influenza A(H7N9) virus, including 11 deaths.
Onset dates range from 17 January to 19 February. Cases range in age from 21 to 78 years, with a median age of 57 years. Of these 29 cases, 22 (76%) are male. The majority (24 cases, 83%) reported exposure to live poultry, slaughtered poultry, or live poultry markets; the exposure history of 5 cases is unknown or with no clear exposure to poultry. Cases were reported from 6 provinces and municipalities: Zhejiang (7), Hunan (7), Jiangsu (6), Guangdong (4), Fujian (3) and Shanghai (2).
Three clusters were reported:
- The first cluster consists of two 35-year-old males (twin brothers) from Jiangsu Province, the onset dates are respectively 19 January and 1 February. Both have no clear known history of exposure to poultry.
- The second cluster consists of a 29-year-old male from Zhejiang Province and a 56-year-old female (son and mother) from Fujian Province. The onset dates are 4 February and 15 February, respectively. Both have history of exposure to live poultry market.
- The third cluster consists of a 21-year-old female and a 26-year-old male (sister and brother) both from Jiangsu Province, the onset dates are 14 February and 19 February, respectively. The brother reported exposure to live poultry. The sister took care of her brother and has no known history of exposure to poultry.
Public health responseThe Chinese Government has taken the following surveillance and control measures:
- strengthening outbreak surveillance and situation analysis;
- reinforcing all efforts on medical treatment; and
- conducting risk communication with the public and dissemination of information.