Wednesday, April 05, 2017

HK CHP Avian Flu Report Week 13


Yesterday was a national holiday in Hong Kong (Qingming Festival) and so the weekly avian flu report we usually see released on Tuesday mornings was published today, instead.  
As has become common in recent weeks, it is essentially a recap - with additional details - on the announcement made the end of the previous week by China's NHFPC (see Friday's  HK CHP Notified Of 17 New H7N9 Cases From The Mainland).

All of this means that the numbers in this report are probably a couple of weeks old, and while the number of new cases being reported from Mainland China has slowed, we continue to see a pretty steady stream of reports. 

Since the start of this 5th epidemic season last October, 566 H7N9 infections have been reported - 558 on the Mainland - plus 8 exported cases (5 in Hong Kong, 2 in Macao & 1 in Taiwan).

Avian Influenza Report

Avian Influenza Report is a weekly report produced by the Respiratory Disease Office, Centre for Health Protection of the Department of Health. This report highlights global avian influenza activity in humans and birds.

Reporting period: March 26, 2017 – April 1, 2017 (Week 13)
(Published on April 5, 2017)

1. Since the previous issue of Avian Influenza Report (AIR), there were 17 new human cases of avian influenza A(H7N9) reported by Mainland China health authorities in Hunan (6 cases), Guangxi (3 cases), Jiangsu (3 cases), Fujian (2 cases), Guizhou (2 cases) and Zhejiang (1 case). Since March 2013 (as of April 1, 2017), there were a total of 1364 human cases of avian influenza A(H7N9) reported globally. Since October 2016 (as of April 1, 2017), 558 cases have been recorded in Mainland China.
2. Since the previous issue of AIR, there were no new human cases of avian influenza A(H5N6). Since 2014 (as of April 1, 2017), 16 human cases of avian influenza A(H5N6) were reported globally and all occurred in Mainland China. The latest case was reported on December 1, 2016.
3. Since the previous issue of AIR, there were two new human cases of avian influenza A(H5N1) from Egypt reported by the World Health Organization (WHO). From 2011 to 2016, 10 to 145 confirmed human cases of avian influenza A(H5N1) were reported to WHO annually (according to onset date). In 2017, there have been so far two cases in Egypt.*

Since only those those ill enough to be hospitalized are generally tested, and H7N9 can produce a wide spectrum of illness - ranging from asymptomatic to severe - the actual number of infections is unknown (see Beneath The H7N9 Pyramid).   

This week's report is the 2nd in a row without any mention of Guangdong Province, which has traditionally been one of the hot spots for H7N9 transmission and was the site of the recent emergence of an HPAI variant of the virus.

Whether this absence is due to delays in reporting - which we've seen in the past - or to a genuine drop in infections, is something we'll be keeping an eye on. The fact that it has been nearly a month since Hong Kong or Macao - which lie adjacent to Guangdong Province - have reported an imported case of H7N9 is a hopeful sign.

With 136 cases this season, Jiangsu Province has been the hardest hit, and last week's   Eurosurveillance: Preliminary Epidemiology & Analysis Of Jiangsu's 5th H7N9 Wave, looked at concerns over suspected increased virulence of the new Yangtze River Delta (LPAI) lineage of the virus, and the possibility that it may be more `heat tolerant' and able to spread during warmer months.

Despite the spike in human cases this winter, and ongoing genetic changes in the virus, the WHO's Risk Assessment remains unchanged:

WHO risk assessment
The number of human infections with avian influenza A(H7N9) in the fifth epidemic wave (i.e. onset since 1 October 2016) is greater than the numbers of human cases reported in earlier waves.

Human infections with the avian influenza A(H7N9) virus remain unusual. Close observation of the epidemiological situation and further characterization of the most recent human viruses are critical to assess associated risk and to adjust risk management measures in a timely manner.

Most human cases are exposed to avian influenza A(H7N9) virus through contact with infected poultry or contaminated environments, including live poultry markets. Since the virus continues to be detected in animals and environments, and live poultry vending continues, further human cases can be expected. Although small clusters of cases of human infection with avian influenza A(H7N9) virus have been reported including those involving patients in the same ward, current epidemiological and virological evidence suggests that this virus has not acquired the ability of sustained transmission among humans. Therefore the likelihood of further community level spread is considered low.

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