Thursday, January 17, 2019

Hong Kong's Flu Express Wk 2: A Rapid Increase In Institutional Outbreaks


We're seeing a highly variable 2018-2019 Northern Hemisphere flu season, with Canada and South Korea kicking off very early, while Russia - which over the past two decades has seen a shift to earlier flu seasons (see Eurosurveillance: Changes In Timing Of Influenza Epidemics - WHO European Region 1996-2016 -  still remains far below their epidemic threshold (see Russia Influenza Surveillance Week 1, 2019).
Last week Hong Kong announced they had passed their epidemic threshold - and like most of the globe - is reporting mostly H1N1, which typically has a greater impact on younger people than does H3N2.
A good illustration of this demographic impact is the chart (above) showing an impressive 30-fold increase in institutional (mostly school) outbreaks in Hong Kong over the previous reporting week.  This is their biggest, and fastest ramp up in recent memory.

Over the past 3 days Hong Kong's CHP has announced investigations into numerous influenza outbreaks, including:
CHP investigates case of severe paediatric influenza A infection and outbreaks of influenza A at primary school and kindergartens

Update on cluster of Influenza A cases in Kowloon Hospital

CHP investigates cases of severe paediatric influenza A infection and outbreaks of influenza A and influenza-like illness at kindergartens

CHP investigates influenza A outbreaks at kindergarten-cum-child care centre and primary school 

One week into their flu season and already hospitals are getting slammed,  with yesterday's average hospital occupancy rate reaching 111%.  With the Chinese New Year's celebration only about 2 weeks away - where millions of families will gather all over Asia - these numbers could continue to rise.

The headlines in the South China Morning Post (SCMP) this morning - just one week into their flu season - highlight the pressures their healthcare system is already under.

Nurses plan protest as Hong Kong’s public hospitals reach flu season breaking point
Medical staff having to work extra shifts and skip meals to care for influx of flu patients
Bed occupancy rate across Hong Kong’s public hospitals reached average of 111 per cent on Wednesday
PUBLISHED : Thursday, 17 January, 2019, 1:26pm

 Some excerpts from today's much longer CHP Flu Express follow:

VOLUME 16, NUMBER 02 (PUBLISHED ON Jan 17, 2019)
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.s.

Local Situation of Influenza Activity (as of Jan 16, 2019)

  • Reporting period: Jan 6 – 12, 2019 (Week 2)The latest surveillance data showed that the local influenza activity increased markedly last week.
  • Currently the predominating virus is influenza A(H1).
  • Children aged under 6 years were particularly affected as reflected by the very high number of outbreaks of influenza-like illness (ILI) in kindergartens and child care centres, as well as
    influenza-associated admission rate in public hospitals among children aged below six years.
  • Among the severe influenza cases in adults, persons 50-64 years constituted a relative higher proportion (36%), as compared with 15% and 20% during the 2017 summer season predominated by influenza A(H3) and the 2017/18 winter season predominated by influenza B respectively.
  • Influenza can cause serious illnesses in high-risk individuals and even healthy persons. Given that seasonal influenza vaccines are safe and effective, all persons aged 6 months or above except those with known contraindications are recommended to receive influenza vaccine to protect themselves against seasonal influenza and its complications, as well as related hospitalisations and deaths.
Global Situation of Influenza Activity In the temperate zone of the northern hemisphere influenza activity continued to increase slowly. In East Asia, influenza season appeared to have started, with predominantly influenza A(H1N1)pdm09 detected. In Europe, influenza activity increased, with both A viruses circulating. In the temperate  zones of the southern hemisphere, influenza activity returned to inter-seasonal levels with exception of some parts in Australia. Worldwide, seasonal influenza A viruses accounted for the majority of detections.
  • In the United States (week ending Jan 5, 2019), influenza activity remained elevated. The proportion of outpatient visits for ILI decreased from 4.0% to 3.5%, but remained above the national baseline of 2.2%. The percent of respiratory specimens testing positive for influenza decreased to 12.72% from 16.58% recorded in the previous week. Influenza A(H1N1)pdm09, influenza A(H3N2), and influenza B viruses continued to co-circulate.
  • In Canada (week ending Jan 5, 2019), influenza activity remained high. The influenza season started in late October which was earlier than in recent years. Laboratory detections for influenza declined from the previous week, suggesting that nationally the influenza season may have reached peak levels in the last week of December. Influenza A was the most common influenza virus, and the majority of these viruses were A(H1N1)pdm09.
  • In the United Kingdom (week ending Jan 6, 2019), there was evidence that influenza was now circulating in the community as activity indicators breached baseline threshold levels at low intensity. The positivity of influenza detection was 16.4%, which was above the baseline threshold of 9.2%.
  • In Europe (week ending Jan 6, 2019), influenza activity continued to increase. 44.6% of sentinel specimens were tested positive for influenza virus. The majority of influenza virus detections were type A. Both influenza A(H3N2) and A(H1N1)pdm09 viruses were detected.
  • In Mainland China (week ending Jan 6, 2019), influenza activity in southern and northern provinces continued to increase, reaching the peak of the influenza season currently. Influenza viruses detected were mainly influenza A(H1N1), followed by influenza A(H3N2), and there were few influenza B(Victoria) and B(Yamagata) detections.
  • In Taiwan (week ending Jan 12, 2018), influenza activity increased significantly and was above the national baseline. Influenza A(H1N1) (43.1%) and A(H3N2) (29.4%) viruses co-circulated in the community in recent four weeks.
  • In Macau (Jan 16, 2019), influenza activity remained at the peak level. The proportions of ILI cases in emergency departments among both adults and children remained at a high level, and were on an
    increasing trend. The proportion of influenza detections reached 42% in the first two weeks of 2019. Influenza viruses detected were influenza A(H1) (75%) and influenza A(H3) (25%).
  • In Japan (week ending Jan 6, 2019), influenza activity continued to increase and the influenza season started in early December. The average number of reported ILI cases per sentinel site increased to 16.30 in the week ending Jan 6, 2019, which was above the baseline level of 1.00. The predominating virus in the past four weeks was influenza A(H1N1)pdm09
(Continue . . . )
During the run up to last year's Chinese New Year's Holiday - during an unusually severe influenza B season - Hong Closed Schools & Called For Stringent NPIs To Combat Flu. According to an EID analysis published last November, the decision was made after the peak of the outbreak, and only had modest effect.
Mitigation of Influenza B Epidemic with School Closures, Hong Kong, 2018


In winter 2018, schools in Hong Kong were closed 1 week before the scheduled Chinese New Year holiday to mitigate an influenza B virus epidemic. The intervention occurred after the epidemic peak and reduced overall incidence by ≈ 4.2%. School-based vaccination programs should be implemented to more effectively reduce influenza illnesses.
Although school closures can be disruptive - particularly to working families -  previous studies have shown a more profound effect can be achieved when the trigger is pulled earlier.

As no two flu seasons are ever alike, a one size-fits-all solution isn't guaranteed to work.  It will be interesting to see what Hong Kong decides to do this year, based on the conflicting results from past school closures.