Thursday, February 22, 2018

Hong Kong Flu Express Wk 7: Flu Remains At A High Level


Although there are some hopeful signs that flu may have finally peaked in Hong Kong, influenza activity remains at a high level, and local schools will resume classes next week after an extended closing for flu and the New Year's Holiday. 

Today's hospital Occupancy report (below) shows a 5% drop over Tuesday's post-holiday 119% peak, although admissions yesterday were still running about 150 over the average for this time of year.

Even with all schools having been closed for two weeks, institutional outbreaks continue to outpace any flu season in recent memory, no doubt inspiring an announcement today from the CHP Public urged to continue their vigilance against influenza as school will soon resume.

Influenza B continues to produce the vast majority of infections, with influenza A (H1N1 & H3N2) making up a minority of cases. Some excerpts from today's Hong Kong Flu Express (week 7) follow:

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 Feb 21, 2018)

Reporting period: Feb 11 – 17, 2018 (Week 7)

  • The latest surveillance data showed that the local influenza activity remained at a high level in the past few weeks. Currently the predominating virus is influenza B.
  • 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.
  • 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.


Influenza-like-illness surveillance among sentinel general outpatient clinics and sentinel private doctors, 2014-18

In week 7, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPCs) was 7.3 ILI cases per 1,000 consultations, which was lower than 8.9 recorded in the previous week (Figure 1, left). The average consultation rate for ILI among sentinel private doctors was 36.4 ILI cases per 1,000 consultations, which was lower than 71.3 recorded in the previous week (Figure 1, right).

Since the start of the 2017/18 winter influenza season in week 2, 373 adult cases of ICU admission/death with laboratory confirmation of influenza were recorded, in which 228 of them were fatal (as of February 21). Among them, 317 patients had infection with influenza B, 29patients with influenza A(H1N1)pdm09, 17 patients with influenza A(H3N2), three patients with influenza C and seven patients with influenza A pending subtype.

  • In comparison, 283, 207 and 88 adult cases were recorded in the same duration of surveillance(six complete weeks) in the 2014/15 winter, 2015/16 winter and 2017 summer seasons respectively, as compared with 327 cases in the current season (Figure 10, left). The corresponding figures for deaths were 208, 89 and 67 in the above seasons, as compared with 195 deaths in the current season (Figure 10, right).


Severe influenza cases of all ages

• Since the start of the current winter influenza season in week 2, 388 severe influenza cases among all ages have been reported, including 230 deaths (as of February 21).

 • Among the adult fatal cases, about 83% had chronic diseases. Both of the two paediatric fatal cases did not have chronic diseases.
• Among patients with laboratory confirmation of influenza admitted to public hospitals in this season (from January 7 to February 21), 2.0% of admitted cases died during the same episode of admission. So far, it was within the historical range between 1.9% (2015/16 winter season) and 3.3% (2015 summer season).


Global Situation of Influenza Activity
  • In Mainland China (week ending Feb 11, 2018), both southern and northern provinces were still in winter influenza season but the activity continued to decrease. The proportion of influenza A detection was higher than that of influenza B. Influenza A(H1N1) and influenza B Yamagata viruses are predominating while levels of influenza A(H3N2) and influenza B Victoria viruses remained low. In southern provinces, the proportion of ILI cases in emergency and outpatient departments reported by sentinel hospitals was 4.7%, lower than that reported in the previous week (5.1%) but higher than that in the corresponding period in 2015-2017 (2.8%, 4.6%, 2.6%). In northern provinces, that proportion was 3.7%, lower than those reported in the previous week (4.2%) and the corresponding period in 2016 (5.1%), but higher than those in the corresponding period in 2015 and 2017 (both were 2.9%). The proportion of influenza detections in the week ending Feb 11, 2018 was 36.4% (65.2% influenza A and 34.8% influenza B).
  • In Macau (as of Feb 21, 2018), the influenza activity has been slowed down but remained at high level. The proportions of ILI cases in emergency departments among adults and children decreased.
  •  In Taiwan (week ending Feb 17, 2018), influenza activity was similar to the previous week and remained at the peak of the season. In the week ending Feb 17, the proportion of ILI cases in emergency department was 17.61% which was above the threshold of 11.4%. The predominating virus was influenza B.
  •  In Japan (week ending Feb 11, 2018), the influenza season has started in late November 2017. The average number of reported ILI cases per sentinel site has decreased to 45.38 in the week ending Feb 11, 2018 from 54.33 in the previous week. It was higher than the baseline level of 1.00. The predominating virus in the past five weeks was influenza B, followed by influenza A(H3N2) and A(H1N1)pdm09.

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