Thursday, February 08, 2018

Hong Kong Flu Express Wk 5: Flu Remains At A High Level


Despite some subtle hints that their Influenza B epidemic may be peaking, Hong Kong's winter flu activity remains at a high level, and yesterday forced the early closure of all schools, a full week before their scheduled Chinese New Year's break.
The wild card here is the upcoming New Year's holiday, also called Chunyun or the Spring Festival travel season. 
This celebration begins about 15 days before the Lunar New Year (Feb 16th this year) and runs for about 40 days total, during which time more than 2 billion passenger journeys will be made (mostly via crowded rail and bus) across Asia.

In Korea it is called Seollal. While in Vietnam it is celebrated as Tết Nguyên Đán ; the Feast of the First Morning.  Tết for short. By whatever name, the Lunar New Year is undoubtedly the most important holiday in all of Asia

Each year it inspires the largest migration of humans on the planet as shops and factories are closed to allow hundreds of millions to flee the big cities and return to their home towns for a few days to attend a reunion dinner with their families - preferably on the eve of the lunar New Year.

Yesterday, in Cross-boundary passenger traffic estimation and arrangements for Lunar New Year festive period, Hong Kong's Immigration Department  estimated that nearly 6 million passengers (including Hong Kong residents and visitors) will pass through Hong Kong's sea, land and air control points in the week running February 15th to 21st.
The concern  is that this annual migration could promote the spread, and mixing, of seasonal flu viruses, either extending or expanding their regular flu season - or worse -  contribute to the spread of avian flu. 
It is not an idle concern, last year Yunnan Province saw their first ever H7N9 infections after a family visited Jiangxi Province over the New Year's holiday. (see Yunnan: 2nd Imported H7N9 Case (Mother of Last Week's Case).

Fortunately, this year, avian flu reports have been greatly subdued.  Although, how long that happy state of affairs will last is anyone's guess.  Also, since Influenza B doesn't reassort with influenza A viruses, this year the risk of seeing an avian-seasonal reassortment should be reduced.

Meanwhile, institutional outbreaks in Hong Kong are running far higher than in any recent flu season, and this winter's epidemic is on track to being their worst since the severe 2014-15 H3N2 season.

Some excerpts from today's 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 Feb 7, 2018)
Reporting period: Jan 28 – Feb 3, 2018 (Week 5)
  • The latest surveillance data showed that the local influenza activity remained at a high level. 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 5, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPCs) was 11.9 ILI cases per 1,000 consultations, which was higher than 9.7 recorded in the previous week (Figure 1, left). The average consultation rate for ILI among sentinel private doctors was 75.4 ILI cases per 1,000 consultations, which was lower than 76.8 recorded in the previous week (Figure 1, right).
Laboratory surveillance, 2014-18
Among the respiratory specimens received in week 5, the positive percentage of seasonal influenza viruses was 24.40%, which was above the baseline threshold of 10.7% but lower than 26.41% recorded in the previous week (Figure 2). The 1805 influenza viruses detected last week included 174 (2.35%) influenza A(H1), 82 (1.11%) influenza A(H3), 1479 (19.99%) influenza B and 70 (0.95%) influenza C.
Influenza-like illness outbreak surveillance, 2014-18
In week 5, 115 ILI outbreaks occurring in schools/institutions were recorded (affecting 607 persons), which was higher than 109 outbreaks recorded in the previous week (affecting 805 persons) (Figure 3). In the first 4 days of week 6 (Feb 4-7, 2018), 88 ILI outbreaks in schools/institutions were recorded (affecting 394 persons). Since the start of the 2017/18 winter influenza season in week 2, 421 outbreaks were recorded (as of February 7).
In comparison, 130, 62 and 93 outbreaks were recorded in the same duration of surveillance (four complete weeks) in the 2014/15 winter, 2015/16 winter and 2017 summer seasons respectively, as compared with 333 outbreaks in the current season (Figure 4).
Severe influenza cases of all ages
• Since the start of the current winter influenza season in week 2, 227 severe influenza cases among all ages have been reported, including 123 deaths (as of February 7).
• Among the adult fatal cases, about 81% 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 7), 1.7% of admitted cases died during the same episode of admission. So far, it was below the historical range between 1.9% (2015/16 winter season) and 3.3% (2015 summer season).

 In Mainland China (week ending Jan 28, 2018), the influenza activity in both southern and northern provinces was still at a high level but on a decreasing trend. In southern provinces, the proportion of ILI cases in emergency and outpatient departments reported by sentinel hospitals was 5.9 %, lower than that reported in the previous week (6.7%) but higher than that in the corresponding period in 2015-2017 (3.2%, 3.1%, 3.3%). In northern provinces, that proportion was 4.9%, lower than that reported in the previous week (5.3%) but higher than that in the corresponding period in 2015-2017 (3.1%, 3.6%, 3.8%). The proportion of influenza detections in the week ending January 28, 2018 was 42.5% (59.5% influenza A and 40.5% influenza B).

 In Macau (week ending Jan 27, 2018), the proportions of ILI cases in emergency departments among adults and children increased. The proportion of influenza detections was 54.9%, higher than 44.6% in the previous week.

 In Taiwan (week ending Feb 3, 2018), influenza activity showed a decreasing trend, but was still at the peak of the season. In the week ending February 3, the proportion of ILI cases in emergency department was 13.85% which was above the threshold of 11.4%. The predominating virus was influenza B.

 In Japan (week ending Jan 28, 2018), the influenza season has started in late November 2017. The average number of reported ILI cases per sentinel site increased slightly to 52.35 in the week ending January 28, 2018 from 51.93 in the previous week, which 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).

(Continue . .. .)

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