Thursday, May 11, 2017

Follow Up On Hong Kong's Flu Resurgence


Credit Hong Kong Flu Express Wk 18














#12,449


Last week, in Hong Kong CHP Reports A Late Season Flu Surge, we looked at reports of severe influenza several weeks after Hong Kong's flu season had supposedly ended.  While Hong Kong is somewhat unique in that it often sees two flu seasons, the `second season' isn't expected until mid-summer.
In response to these reports, the CHP and the Hospital Authority reactivated their  enhanced surveillance for severe seasonal influenza cases among patients aged 18 or above on May 5th, 2017.

Today's Flu Express (week 18) provides us with the first (partial) week of surveillance (May 5th-10th), and we learn that during that time there were 14 flu-related ICU admissions and 6 deaths. Of 14 severe cases, half were identified as H3N2, 3 were H1N1, one was Influenza B, and 3 are influenza A with subtype pending.

The graphic as the top of the page shows that activity on the far right of the chart.


VOLUME 14, NUMBER 18 (PUBLISHED ON May 11, 2017)

Surveillance of severe influenza cases

 
(Note: The data reported are provisional figures and subject to further revision)
Since the activation of the enhanced surveillance for severe influenza infection on May 5, 2017, a total of 14 severe cases (including 6 deaths) were recorded cumulatively (as of May 10) (Figure 9). These included:

  • 14 cases (including 6 deaths) among adult patients aged 18 years or above. Among them, seven patients had infection with influenza A(H3N2), three patients with influenza A(H1N1)pdm09, one patient with influenza B and three patients with influenza A with subtype pending. Two (14.3%) were known to have received the influenza vaccine for the 2016/17 season. Among the six fatal cases, one (16.7%) were known to have received the influenza vaccine. In the winter season in early 2017, 66 adult severe cases (including 41 deaths) were filed.
  • No cases of severe paediatric influenza-associated complication/death. To date in 2017, 8 paediatric cases (including one death) were filed.
  • Enhanced surveillance for severe seasonal influenza (Aged 18 years or above)
  • In the last 2 days of week 18 and the first 4 days of week 19 (May 5 to 10), 6 cases and 8 cases of influenza associated ICU admission/death were recorded respectively. Among all the cases, 6 cases were fatal.
  • Surveillance of severe paediatric influenza-associated complication/death (Aged below 18 years)
  • In week 18 and the first 4 days of week 19 (May 7 to 10), there were no new cases of severe paediatric influenza-associated complication/death.

Influenza, particularly in Hong Kong, can be erratic.  As an international city, HK receives visitors from all over the world, any of whom could bring influenza (or any other virus) in with them.  Hong Kong also hosts tens of thousands of visitors and/or workers from Mainland China each day.  
Like a canary in a coal mine, influenza surveillance in Hong Kong can often provide us with an early warning of a change in these viruses, so we watch these reports with interest.  
So far, the good news is this surge appears to be due to a mixture of seasonal H3N2 and H1N1, and not something more exotic.  Should that change, the CHP will quickly let us know.

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