One of the hallmarks of China's H7N9 outbreak's - at least during the first couple of epidemic waves (2013-2014) - was how few family clusters we saw reported. With few exceptions (see BMJ: `Probable Person-to-Person Transmission’ Of H7N9) close contacts of infected cases stayed virus free.
The vast majority of human H7N9 cases in China have been described as individual, widely scattered and usually linked to live bird exposure
H7N9's reputation has slowly changed over the past few months, as we've recently learned of a couple of nosocomial outbreaks of H7N9 and several family clusters have been announced.
First in EID Journal: Nosocomial Co-Transmission Of H7N9 & H1N1pdm09 which involved 2 patients at a hospital in Zhejiang Province in 2014, and then in NEJM: Probable Hospital Cluster of H7N9 - China, 2015, a cluster involving a patient and two doctors, again in Zhejiang Province.
In last month's WHO H7N9 Update Details 3 Clusters In China, we saw - out of 29 cases reported during February - 3 family clusters (see below). While the onset dates and details are suggestive of H-2-H transmission, shared or environmental exposures are also possible.
- 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.
To this small, but growing list, we can another cluster reported by Xinhua News and confirmed by Hong Kong' CHP last night, this time a mother-son combination from Fujian Province.
Two reports, then I'll return with a bit more:
East China province reports two H7N9 cases
Source: Xinhua 2016-04-17 22:49:41 [More]
NANCHANG, April 17 (Xinhua) -- Two human H7N9 cases have been confirmed in east China's Jiangxi Province, local health authorities said on Sunday.
The two patients are a 43-year-old woman surnamed Huang and a 23-year-old man surnamed Xiao. They are a mother and son, said the provincial health and family planning commission. Both Xiao and Huang are natives of Taihe County in the city of Ji'an. They were working in Jinjiang City, Fujian Province before they found they had infected the disease. Then, they went back to seek treatment in Jiangxi.
They tested positive for H7N9 on Saturday. They are being treated in a hospital in Nanchang, capital of Jiangxi, and both are in stable condition now, according to the commission.
H7N9 is a bird flu strain first reported to have infected humans in March 2013 in China. It is most likely to strike in winter and spring.
CHP closely monitors two additional human cases of avian influenza A(H7N9) in Mainland
The Centre for Health Protection (CHP) of the Department of Health (DH) is today (April 18) closely monitoring two additional human cases of avian influenza A(H7N9) in the Mainland, and again urged the public to maintain strict personal, food and environmental hygiene both locally and during travel.
According to the Health and Family Planning Commission of Jiangxi Province, the female patient aged 43 and her son aged 23 live in Taihe, Ji'an, and work in Jinjiang, Fujian. They have been hospitalised in Nanchang in stable condition.
From 2013 to date, 738 human cases of avian influenza A(H7N9) have been reported by the Mainland health authorities.
The DH's Port Health Office conducts health surveillance measures at all boundary control points. Thermal imaging systems are in place for body temperature checks on inbound travellers. Suspected cases will be immediately referred to public hospitals for follow-up.
(Continue . . .)
Noticeably absent from these reports are onset dates or any mention of poultry or live bird market exposure. Perhaps additional details will emerge later.
While live bird exposure was found to be a strong risk factor in China's H7N9 case-control study, and noted for the majority of the 700+ cases we've seen, for some cases a plausible route of exposure is simply never identified.
Overall, the number of H7N9 cases reported this winter by China is down markedly over previous winters. Whether this indicates changes in surveillance and reporting, or reflects better biosecurity at live bird markets and a reduction in human infection, isn't clear.
While China's overall H7N9 trends (no large clusters, no sustained community transmission, fewer exported cases & lower case count) for the winter of 2015-16 all seem positive, this apparent increase in small clusters bears watching.