Hong Kong Reports Another Increase In Their Late Season Flu Surge

Credit HK Flu Express

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After reporting a brief dip last week (see here) Hong Kong's unexpected late season flu surge, which began 6 weeks ago - two weeks after their flu season appeared to have ended - has increased again. 

So far, at least 116 severe cases (including 82 deaths) have been reported since May 5th, including 10 severe pediatric cases (2 of which were fatal). 

This second surge - in just under 50 days - has now reported twice as many flu fatalities as were reported during the first four months of 2017 (n=41). The number of ICU admissions is nearly doubled, as well.

While Hong Kong often sees a second flu season each year (see Seasonality of Influenza A(H3N2) Virus: A Hong Kong Perspective (1997–2006)) - that usually comes in late summer - not hot on the heels of the last flu season, which appeared to be over in mid April.

Despite their unseasonal appearance, and severity, the viruses being reported by Hong Kong's CHP appear to be standard seasonal flu strains; H3N2, H1N1, Influenza B and C. 

Lab surveillance in this latest report indicate: 81.8% (H3N2), 10.8% (H1N1), 5.2% (B) and 2.2% (C) - reflecting a small increase in the percentage of H3N2 detections over last week, and a moderate drop in the percentage of H1N1. 

Some excerpts from today's Flu Express, then I'll return with a postscript.

 VOLUME 14, NUMBER 24 (PUBLISHED ON Jun 22, 2017)
 
FLU EXPRESS

Flu Express is a weekly report produced by the Respiratory Disease Office of the Centre for Health Protection. It monitors and summarizes the latest local and global influenza activities.

Local Situation of Influenza Activity (as of Jun 21, 2017)

Reporting period: Jun 11 – 17, 2017 (Week 24)

• The latest surveillance data showed that the local influenza activity has increased when compared with the previous week.
• The Centre for Health Protection (CHP) has collaborated with the Hospital Authority (HA) and private hospitals to reactivate the enhanced surveillance for severe seasonal influenza cases (i.e. influenza-associated admissions to intensive care unit or deaths) among patients aged 18 or above since May 5, 2017. As of Jun 21, 106 severe cases (including 80 deaths) were recorded. Separately, ten cases of severe paediatric influenza-associated complication/death (including two deaths) (aged below 18 years) were recorded in the same period.
•  Apart from adopting personal, hand and environmental hygiene practices against respiratory illnesses, those members of the public who have not received influenza vaccine are urged to get vaccinated as soon as possible for personal protection.

(SNIP)

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 116 severe cases (including 82 deaths) were recorded cumulatively (as of Jun 21) (Figure 9). These included:

• 106 cases (including 80 deaths) among adult patients aged 18 years or above. Among them, 83 patients had infection with influenza A(H3N2), 16 patients with influenza A(H1N1)pdm09, six patients with influenza B and one patient with influenza A without subtype. Thirty-five (33.0%) were known to have received the influenza vaccine for the 2016/17 season. Among the 80 fatal cases, 33 (41.3%) were known to have received the influenza vaccine. In the winter season in early 2017, 66 adult severe cases (including 41 deaths) were filed.
• Ten cases (including two deaths) of severe paediatric influenza-associated complication/ death. Nine (90.0%) cases did not receive the influenza vaccine for the 2016/17 season. To date in 2017, 18 paediatric cases (including three deaths) were filed.
  Enhanced surveillance for severe seasonal influenza (Aged 18 years or above)

• In week 24, 16 cases of influenza associated ICU admission/death were recorded, in which 13 of them were fatal. In the first 4 days of week 25 (Jun 18 to 21), 12 cases of influenza associated ICU admission/death were recorded, in which nine of them were fatal.

Surveillance of severe paediatric influenza-associated complication/death (Aged below 18 years)

• In week 24, there was one case of severe paediatric influenza-associated complication. In the first 4 days of week 25 (Jun 18 to 21), no cases of severe paediatric influenza-associated complication/death were reported.

(Continue . . . )

While nowhere near as pronounced, Taiwan has reported a noticeable uptick in severe influenza cases over the past 6 weeks as well (see chart below).  Elsewhere around the world, we aren't hearing a lot about seasonal influenza, although the number of flu cases in Australia are slowly increasing as winter sets in.
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Credit Taiwan CDC

Hong Kong runs their flu vaccination program in the fall, primarily focused on high risk groups like pregnant women and the elderly, and presumably by now some of last year's protective effects have begun to wane. 

Add in the inevitable antigenic drift of flu viruses over time, and that may account - at least in part - for the increased flu toll we are seeing.

Today Hong Kong's CHP has announced plans for next fall's flu vaccination program, set to begin in October (see Seasonal influenza vaccination programmes in 2017/18 to be launched), targeted towards the following priority groups. 

Until then, Hong Kong residents are being encouarged to practice good flu hygiene, including:

• Wash hands frequently with liquid soap and water, especially before touching the mouth, nose or eyes, or after touching public installations such as handrails or door knobs.
• When hands are not visibly soiled, clean them with 70 - 80% alcohol-based handrub as an effective alternative.
• Cover nose and mouth when sneezing or coughing, and wash hands thoroughly afterwards.
• Dispose of soiled tissue paper properly in a lidded rubbish bin.
• Put on a surgical mask when having respiratory symptoms.
• Maintain good indoor ventilation.
• When influenza is prevalent, avoid going to crowded or poorly ventilated public places; high-risk individuals may consider putting on surgical masks while in such places.
• Maintain a balanced diet, exercise regularly, take adequate rest, do not smoke and avoid overstress.

Meanwhile, we'll continue to watch the Southern Hemisphere's flu season closely to see if its severity is similarly heightened, and how all this might affect the Northern Hemisphere this coming fall.