Hong Kong’s Centre for Health Protection weekly Avian Influenza Report published on August
1 is the first weekly report in 2017 with no reported human H7N9 cases from the
Republic of China. The last weekly Avian
Influenza Report with no reported H7N9 cases was previously published on
December 1, 2016. In the intervening 8 months more than 750 human H7N9 cases were
reported from China. This is an extremely large number of human infections in a
short time period.
Human cases of H7N9 were first identified and reported from China
late in the 2012-2013 influenza season. Since then, there have been several
waves of human H7N9 infections generally corresponding with seasonal influenza
outbreaks. Although human cases of H7N9 have been sporadically reported over
the past four years, the 750+ cases reported in the last eight months represent
about 49% of all reported H7N9 cases. To date, all human infections have
occurred in China although some individuals infected in China were identified
in other countries.
Chart: Number of human H7N9
cases by influenza season.
As depicted in the maps below, between 13 and 16 provinces,
autonomous areas, or municipalities were reporting H7N9 cases during these previous
waves on a seasonal basis. This recent wave with over 750 cases, the 2016-2017
influenza season, struck China particularly hard. All provinces, autonomous
areas, municipalities, or special administrative regions in China with the
exception of Hainan, Heilongjiang, Qinghai, and Ningxia Hui reported at least
one human H7N9 case during the past influenza season.
Map: Distribution of human H7N9 cases in China in early
2013.
Map: Distribution of human H7N9 cases in China in the
2013-2014 influenza season.
Map: Distribution of human H7N9 cases in China in the
2014-2015 influenza season.
Map: Distribution of human H7N9 cases in China in the 2015-2016
influenza season.
Map: Distribution of human H7N9 cases in China in the
2016-2017 influenza season.
Domestic poultry may soon be infected in adjoining countries
of Myanmar, Laos, and Vietnam. Human
cases from these countries in the future would not be surprising. With the next
influenza season officially starting in a few weeks, we can anticipate that
additional human H7N9 cases will be reported from China in the upcoming influenza
season.
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