Friday, February 16, 2018

FluView Week 6: Influenza Remains At An Elevated Level


https://www.cdc.gov/flu/weekly/













#13,153


The CDC's FluView Week 6 report is out, and it shows that this year's season  - while still greatly elevated - may be trying to plateau.  As the chart above illustrates, visits to doctors for flu-like illnesses continue to run very near the peak levels seen during the 2009 pandemic.

Even as the number H3N2 cases begins to decrease, the number of influenza B cases continues to rise, this past week making up more than 1/3rd (33.8%) of all flu positive samples tested by the CDC.

https://www.cdc.gov/flu/weekly/

Hospitalizations continue to set records (67.4 per 100,000), already  exceeding the end-of-season totals seen during the severe 2014-15 flu season when roughly 700,000 people were hospitalized.

With another 6 weeks or more of flu to go, these numbers could go considerably higher.


And tragically, another 22 pediatric flu-related deaths were reported during the past week, although as often is the case, some of these deaths are delayed reports from earlier in the season.

https://www.cdc.gov/flu/weekly/
.
Some highlights from today's much larger report follow.


2017-2018 Influenza Season Week 6 ending February 10, 2018

All data are preliminary and may change as more reports are received.

Synopsis:

During week 6 (February 4-10, 2018), influenza activity remained elevated in the United States.
  • Viral Surveillance: The most frequently identified influenza virus subtype reported by public health laboratories during week 6 was influenza A(H3). The percentage of respiratory specimens testing positive for influenza in clinical laboratories remained elevated.
  • Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was above the system-specific epidemic threshold in the National Center for Health Statistics (NCHS) Mortality Surveillance System.
  • Influenza-associated Pediatric Deaths: Twenty-two influenza-associated pediatric deaths were reported.
  • Influenza-associated Hospitalizations: A cumulative rate of 67.9 laboratory-confirmed influenza-associated hospitalizations per 100,000 population was reported.
  • Outpatient Illness Surveillance:The proportion of outpatient visits for influenza-like illness (ILI) was 7.5%, which is above the national baseline of 2.2%. All 10 regions reported ILI at or above region-specific baseline levels. New York City, the District of Columbia, Puerto Rico and 43 states experienced high ILI activity; two states experienced moderate ILI activity; three states experienced low ILI activity; and two states experienced minimal ILI activity.
  • Geographic Spread of Influenza:The geographic spread of influenza in Puerto Rico and 48 states was reported as widespread; one state reported regional activity; the District of Columbia, Guam and one state reported local activity; and the U.S. Virgin Islands reported no activity.
                 (Continue . . . )

As always, it isn't too late to get the flu shot.  And with influenza B and H1N1 rising, it could still offer some valuable protection.  But most of all, now is the time to practice good flu hygiene. 

Stay home if you are sick, avoid crowds, wash your hands frequently, and cover your coughs and sneezes. 
While we may have reached the peak of this flu season, there is undoubtedly a good deal of flu in store for the next few weeks.




The `Fog Of Flu' On Novel H7N4














#13,152


Two days ago, in Jiangsu China Reports 1st Novel H7N4 Human Infection, we learned of the first known human infection with a novel H7N4 virus via information provided to Hong Kong's CHP from Mainland China

While not available at the time - since then China's NHFPC has posted a short (translated) statement (see below) on their website.   

National Health and Family Planning Commission confirmed case of human infection of H7N4 cases

Published: 2018-02-14
National Health and Family Planning Commission February 13, 2018 confirmed case of human infection of H7N4 avian influenza (referred to cases of human infection with H7N4).

Tang patient, female, 68 years old, live in Liyang City, Jiangsu Province, has a history of contact with live poultry before the onset. Onset December 25, 2017, after a "severe pneumonia" hospitalization, January 22, 2018 cured. Jiangsu Provincial Center for Disease Control samples tested H7N4 positive patients with viral nucleic acid, and confirmed by the Chinese Center for Disease Control review. National Health and Family Planning Commission experts, combined with clinical manifestations, epidemiological investigation and laboratory test results, diagnose cases of human infection of H7N4.

HEALTH health department in accordance with the relevant plans and technical solutions for effective treatment of cases, epidemiological investigation, the close contacts and epidemic emergency management disposal. 28 cases of close contacts found no abnormalities, medical observation has been lifted.

Experts suggest that the public in their daily lives should avoid contact with sick or dead poultry, try to avoid direct contact with live poultry. History of contact with poultry and have fever and respiratory symptoms, should be approaching medical institutions for treatment, and the initiative to inform poultry exposure history to the doctor.
Although there have been copious media reports over the past two days, all of them appear to be based on this statement and the announcement from Hong Kong's CHP.
Surprisingly, we've really learned nothing new in the past 48 hours.
I say `surprisingly', because five years ago - within the first 48 hours after the first H7N9 cases were announced (see China: Two Deaths From H7N9 Avian Flu) - we were flooded with updates from a variety of official sources, including:
WHO: FAQ On H7N9
WHO: Update On H7N9 Virus 

Hong Kong: SFH On H7N9

More Details Emerge On Shanghai H7N9 Case 
Just a little more than 48 hours after the first announcement we were already getting preliminary information about this this novel flu's sequences.
Nature: Declan Butler On The H7N9 Virus Sequences
Webby On H7N9: `Clear Evidence Of Mammalian Adaptation’

Of course, the difference in 2013 was there were multiple cases reported in Shanghai and Anhui province, lending a greater degree of urgency to those reports.  With H7N4, we only have one case (so far)

While I'm hopeful we'll get some information on the genetic sequences of this novel virus over the next few days, with the Lunar New Year celebrations in full swing across Asia, I'm not terribly optimistic that we will hear much until next week.


HHS/CDC Press Conference On Active Flu Season

https://www.youtube.com/watch?v=OeNyLGlNryA
https://www.youtube.com/watch?v=OeNyLGlNryA














#13,151


Late yesterday afternoon the HHS announced a live video press conference would be held at 4:30pm EDT on this year's ongoing severe flu season which would feature HHS Secretary Alex Azar, Acting CDC Director Anne Schuchat, Surgeon General Jerome Adams, and a number of other public health officials.
Since the notice went out so late (I received mine at a quarter to 3), I imagine very few people had time to adjust their schedule to watch. Luckily, a video is already up on the HHS YouTube Channel. 
While not providing any specifics on what we might expect from today's weekly FluView report, officials - after discussing yesterday's MMWR report (see Interim Estimates of 2017–18 Seasonal Influenza Vaccine Effectiveness (VE))the panel continued to urge anyone who hasn't yet been vaccinated to get the shot.
The video conference lasts just under 20 minutes, and also stressed the need to maintain good flu hygiene, and to seek medical advice early for cases of severe flu, or flu in high risk individuals. 
We won't know until later today whether this year's flu season has peaked, or is still on the ascendant, but either way there are almost certainly several more weeks of heavy flu activity ahead.  Additionally, as H3N2 wanes, we may see a surge in Influenza B or H1N1 (or both).
So far there is no notice posted on the CDC Media site of a CDC presser today, but those are often announced the morning of, and so we may still get one later today. 
Either way, all eyes will be on today's FluView report, which I hope to have up before noon (EDT).

Thursday, February 15, 2018

MMWR: Interim Estimates of 2017–18 Seasonal Influenza Vaccine Effectiveness (VE) — US Feb. 2018













#13,150

Two weeks ago in Eurosurveillance: Early Season Flu Surveillance & Vaccine Effectiveness (VE) - Canada, we saw estimates of Canada's VE with their H3N2 component providing only 17% protection, while their influenza B  component produced  a respectable 55%, even though the trivalent shot often used in Canada contained a Victoria strain this year, suggesting some cross protection.
While similar to what we've seen this year, Canada's flu season has featured a higher percentage of influenza B infections, and a less diverse set of H3N2 viruses than reported by the CDC.
Today, the CDC's MMWR has a preliminary analysis of the effectiveness of U.S. vaccines halfway through the flu season, and while similar to the Canadian results, nevertheless shows some interesting differences. According to today's report:
VE was estimated to be 25% (CI = 13% to 36%) against illness caused by influenza A(H3N2) virus, 67% (CI = 54%–76%) against A(H1N1)pdm09 viruses, and 42% (CI = 25%–56%) against influenza B viruses.
The overall U.S. VE (Vaccine Effectiveness) against both A & B subtypes was 36% (compared to Canada's 42%). Some age groups however - notably adolescents (9-17), and adults 50 and older - showed no statistically significant protection from the vaccine.
One bright spot is that kids aged 6 months through 8 years saw as much as 59% protection from this year's vaccine. 
The VE against influenza B (42%) - given the 55% VE from Canada and our greater use of quadrivalent vaccines - came in lower than I think most of us were expecting. Protection ranged from a respectable 50% for those aged 18-64, to a modest 25% for those 65+.
The best performance was against H1N1, but since that has been a minor player in this year's flu season, it has done little to bolster the overall VE numbers.
These are preliminary numbers, and are subject to revision as more data comes in. We'll get a more complete analyses after the flu season has ended.
While this year's vaccine may have produced lackluster results there is some evidence that even when it doesn't prevent the flu, it may reduce the severity of one's illness (see CID Journal: Flu Vaccine Reduces Severe Outcomes in Hospitalized Patients).
That said, we desperately need better flu vaccines.  While some progress has been made (quadrivalent vaccines, high-dose & adjuvanted vaccines) much more needs to be done (see CIDRAP: The Need For `Game Changing’ Flu Vaccines).

I've only included some excerpts from a much longer, far more detailed report.  Follow the link to read it in its entirety.
Interim Estimates of 2017–18 Seasonal Influenza Vaccine Effectiveness — United States, February 2018

Weekly / February 16, 2018 / 67(6);180–185

Brendan Flannery, PhD1; Jessie R. Chung, MPH1; Edward A. Belongia, MD2; Huong Q. McLean, PhD2; Manjusha Gaglani, MBBS3; Kempapura Murthy, MPH3; Richard K. Zimmerman, MD4; Mary Patricia Nowalk, PhD4; Michael L. Jackson, PhD5; Lisa A. Jackson, MD5; Arnold S. Monto, MD6; Emily T. Martin, PhD6; Angie Foust, MS1; Wendy Sessions, MPH1; LaShondra Berman, MS1; John R. Barnes, PhD1; Sarah Spencer, PhD1; Alicia M. Fry, MD1


In the United States, annual vaccination against seasonal influenza is recommended for all persons aged ≥6 months (1). During each influenza season since 2004–05, CDC has estimated the effectiveness of seasonal influenza vaccine to prevent laboratory-confirmed influenza associated with medically attended acute respiratory illness (ARI). 

This report uses data from 4,562 children and adults enrolled in the U.S. Influenza Vaccine Effectiveness Network (U.S. Flu VE Network) during November 2, 2017–February 3, 2018. During this period, overall adjusted vaccine effectiveness (VE) against influenza A and influenza B virus infection associated with medically attended ARI was 36% (95% confidence interval [CI] = 27%–44%).
Most (69%) influenza infections were caused by A(H3N2) viruses. VE was estimated to be 25% (CI = 13% to 36%) against illness caused by influenza A(H3N2) virus, 67% (CI = 54%–76%) against A(H1N1)pdm09 viruses, and 42% (CI = 25%–56%) against influenza B viruses. 

These early VE estimates underscore the need for ongoing influenza prevention and treatment measures. CDC continues to recommend influenza vaccination because the vaccine can still prevent some infections with currently circulating influenza viruses, which are expected to continue circulating for several weeks. Even with current vaccine effectiveness estimates, vaccination will still prevent influenza illness, including thousands of hospitalizations and deaths. Persons aged ≥6 months who have not yet been vaccinated this season should be vaccinated.
(SNIP).

Discussion

Early and widespread influenza activity during the 2017–18 influenza season provided the opportunity to estimate interim VE against several circulating influenza viruses, including the predominant A(H3N2) virus. These interim estimates reflect ongoing challenges with the A(H3N2) vaccine component since the 2011–12 season. 

The interim estimate of 25% VE against A(H3N2) viruses this season indicates that vaccination provided some protection, in contrast to recently reported, nonsignificant interim estimates of 17% from Canada and 10% from Australia (4,5) and is similar to final (32%) VE estimates in the United States against A(H3N2) viruses during 2016–17§ (6).

However, among children aged 6 months through 8 years, the interim estimates against any influenza and A(H3N2) virus infection were higher; the risk for A(H3N2) associated medically-attended influenza illness was reduced by more than half (59%) among vaccinated children. 

Also, with interim VE estimates of 67% and 42% against influenza A(H1N1)pdm09 and B viruses, respectively, vaccination provided substantial protection against circulating A(H1N1)pdm09 viruses, as well as moderate protection against influenza B viruses predominantly belonging to the B/Yamagata lineage, the second influenza type B component included in quadrivalent vaccines. 

(SNIP)
What is added by this report?
 
So far this season, influenza A(H3N2) viruses have predominated, but other influenza viruses are also circulating. Based on data from 4,562 children and adults with acute respiratory illness enrolled during November 2, 2017–February 3, 2018, at five study sites with outpatient medical facilities in the United States, the overall estimated effectiveness of the 2017–18 seasonal influenza vaccine for preventing medically attended, laboratory-confirmed influenza virus infection was 36%.

What are the implications for public health practice?

CDC continues to monitor influenza vaccine effectiveness. Influenza vaccination is still recommended; vaccination reduces the risk for influenza illnesses and serious complications. Treatment with influenza antiviral medications, where appropriate, is especially important this season.

(Continue . . . )

UK: DEFRA Avian Flu In Europe Update -Feb 14th

#13,149



Although Europe hasn't seen anything like last year's record H5N8 epizootic, they continue to report scattered (reassorted) H5N6 detections in wild birds, and a smattering of LPAI H5 outbreaks in poultry in France. 
The pattern and spread of avian influenza continues to be enigmatic and unpredictable, with some regions - like the Middle East and parts of Asia - seeing high yearly activity, with others regions (like Europe and North America) only reporting intermittent flare ups.  
This winter's respite - while welcome - isn't guaranteed to last, however.This year's H5N6 activity seems on par with what Europe saw when HPAI H5N8 first arrived in the winter of 2014-15.  Eighteen months later, Europe saw their biggest avian epizootic in history.
While past performance is not necessarily a predictor of future results, it is safe to say that avian flu has a consistent track record of finding ways to surprise us.
Some excerpts from today's DEFRA report follow:

Situation Assessment #2
 

Findings of H5N6 HPAI in wild birds in UK/Ireland and LPAI in poultry in France 14th February 2018 (Version 2)

 Ref: VITT/1200 Avian Influenza in Europe

Disease report
An emerging reassortant H5N6 highly pathogenic avian influenza (HPAI) virus has been circulating in wild birds in NW Europe in recent months (Defra, 2018). This is an update on the current findings for HPAIV H5N6 in the UK and Europe, and also includes an assessment of a number of outbreaks of low pathogenicity avian influenza virus (LPAIV) reported recently in poultry across France.
It is important to note that to date there have still been no detections of H5N6 HPAI in poultry, either the commercial or non-commercial sectors in the UK. The UK is therefore still officially free of HPAI.
The only outbreak in commercial poultry was detected in Netherlands in December 2017 and was swiftly controlled with no secondary spread.
This report is to inform readers of the ongoing likelihood of more findings in wild birds and the need for strong biosecurity to continue to prevent incursions into poultry farms and backyard poultry.
Situation assessment
Previously there have been six findings of HPAIV H5N6 in wild birds in England, but none in Wales, Scotland or Northern Ireland, despite widespread testing of wild birds. Since the last report (January 2018), there have been a further five outbreaks in wild waterbirds in England. The recent findings are:
1. The River Thames at Windsor, Berkshire –five (out of seven) mute swans (Cygnus olor)
2. Hampton Water in Surrey – two unspecified avians
3. Thames river at Kingston, Greater London – one mute swane
4. Rye Mead RSPB site, Hertfordshire – one tufted duck (Aythya fuligula)
5. Napton Reservoir, Warwickshire – one mute swan
6. Lake near Uffington, Oxfordshire - one mute swan
This takes the current total of events with HPAI H5N6 in wild birds in England to 12. As with the previous wild bird events, these findings are at sites with high numbers of waterfowl and other water birds. To date preliminary results indicate that a single strain of H5N6 HPAI is associated with these infections.
The wild waterfowl migration to the UK will now have peaked for this winter in terms of numbers of overwintering waterfowl although the birds will remain at their wintering sites till next month at least, before returning to their breeding grounds in late March/April.
Wild bird surveillance continues and the map below shows the locations of samples taken for testing from found dead wild birds. These are locations rather than individual birds and therefore there may be more than one bird sampled at each location.
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/681747/avian-flu-wild-birds-H5N6-180213.pdf


In addition the first finding of H5N6 HPAI has been reported in Ireland in a white tailed sea eagle (Haliaeetus albicilla) found dead on the shore of Lough Derg in County Tipperary on 31 January 2018. The bird had been part of a re-introduction project and its tracking data suggests that it had been in the immediate area where it was found dead since 23 January. This area holds large numbers of waterbirds (wildfowl and waders) in winter. The dead eagle was a juvenile female hatched at a nest near Mountshannon, Co. Clare, in July 2017. White-tailed eagles both hunt and scavenge waterbirds and could have been infected through this route.
The Republic of Ireland Government have advised the poultry industry to increase biosecurity measures, but are not considering compulsory confinement of birds at this time, although the situation will be reviewed over the next few days.
Between December and February, four cases of H5N3 LPAI and five of H5 LPAI were reported in commercial duck farms in Gers, Loire Atlantique, Lot and Garonne, Morbihan and Vendee regions, and two H5N3 HPAI in turkey breeding farms in Maine et Loire, west and southwest France. The infected ducks did not present any clinical signs, the infection being detected by screening prior to moving into a gavage unit. In addition, a case of H5N2 LPAI was also detected in fattening ducks in the Landes region. Mutation of H5 LPAI to HPAI is a relatively rare event, but further virus diversity may arise through LPAI viruses reassorting with HPAI strains (especially in wild waterfowl populations), where both are circulating, as suggested for the emergence of the H5N6 HPAI strain in Europe, so the early detection of LPAI virus strains in a region of high poultry density where there are multiple contact routes is important and these latest detections show that the surveillance in France is working. Previous incursions and maintenance of LPAI in these wider regions in recent years led to mutation to HPAI with significant subsequent effects on duck production sectors in particular.
Conclusion
The EURL at Weybridge has the necessary diagnostic capability for these strains of virus, whether low or highly pathogenic.
Given that HPAIV H5N6 infection is now present in wild birds at a number of sites across England, the probability that further events will occur in wild birds in the UK is assessed to remain as “HIGH”. It is not possible to be certain at what time point in the H5N6 epidemic curve these current wild bird cases represent.
Thus, further outbreaks could include as yet undetected ongoing infections at other sites in the UK and also future infections through movement of birds from currently-infected sites to new sites. Since the wild waterbird migration has peaked it is now less likely that H5N6-infected birds will be entering the UK from Europe but local movement between sites may be influenced by colder weather. Indeed, as the birds start to migrate north next month, some cases may occur further north in the UK. The presence of LPAIV in western France currently presents a “LOW” risk of entry to the UK through wild birds. This is because LPAIV has not yet been detected in wild birds in France and birds will not be migrating north from France until April/May.
On the basis of the presence of multiple H5N6-infections in wild birds, and the HIGH risk of further wild bird findings, Avian Influenza Prevention Zones are now in place across England and Wales meaning that poultry keepers must maintain enhanced biosecurity (excluding housing, but using every other means to prevent contact with wild birds). The risk of introduction of infection onto individual poultry premises in the UK remains “LOW” for those poultry farms which have strong biosecurity measures in place, but “MEDIUM” for those with poor biosecurity.

We strongly recommend that all poultry keepers (including backyard keepers) should familiarise themselves with government guidance on good biosecurity and how to report suspicion of disease appropriately.

Hong Kong Flu Express Wk 6: Flu Remains At A High Level


Severe Flu Cases - HK Flu Express Week 6












 #13,148


Despite some fluctuating numbers the past couple of weeks, Hong Kong's winter flu activity remains at a high level, and last week forced the early closure of all schools, a full week before their scheduled Chinese New Year's break.
This holiday coincides with the Spring Festival travel season, which began about 2 weeks before the Lunar New Year (tomorrow, Feb 16th) 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.
Last week, 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 each year 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.
Despite yesterday's surprise announcement of the first H7N4 human infection, avian flu reports this winter have been greatly subdued.  Also, since Influenza B - which has been the dominant seasonal flu virus reported this winter - doesn't reassort with influenza A , this year the risk of seeing an avian-seasonal reassortment should be reduced.

While influenza may have peaked in Hong Kong, institutional outbreaks are running far higher than in any recent flu season, and this winter's epidemic is on track to equal or exceed the severe 2014-15 H3N2 season (see comparison chart below).

We'll have to wait a couple of weeks to see what impact - if any - this weekend's Lunar New Year celebrations will have on the trajectory of this year's epidemic.

Some excerpts from this week's HK Flu Express.  

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 14, 2018)
Reporting period: Feb 4 – 10, 2018 (Week 6)
  • 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 6, the average consultation rate for influenza-like illness (ILI) among sentinel general outpatient clinics (GOPCs) was 8.9 ILI cases per 1,000 consultations, which was lower than 11.9 recorded in the previous week (Figure 1, left). The average consultation rate for ILI among sentinel private doctors was 71.3 ILI cases per 1,000 consultations, which was lower than 75.4 recorded in the previous week (Figure 1, right).


Laboratory surveillance, 2014-18
Among the respiratory specimens received in week 6, the positive percentage of seasonal influenza viruses was 24.14%, which was above the baseline threshold of 10.7% but lower than 24.65% recorded in the previous week (Figure 2). The 2016 influenza viruses detected last week included 269 (3.22%) influenza A(H1), 76 (0.91%) influenza A(H3), 1607 (19.25%) influenza B and 64 (0.77%) influenza C.
https://www.chp.gov.hk/files/pdf/fluexpress_week06_15_02_2018_eng.pdf

Influenza-like illness outbreak surveillance, 2014-18
In week 6, 105 ILI outbreaks occurring in schools/institutions were recorded (affecting 453 persons), which was lower than 115 outbreaks recorded in the previous week (affecting 625 persons) (Figure 3). In the first 4 days of week 7 (Feb 11-14, 2018), 22 ILI outbreaks in schools/institutions were recorded (affecting 114 persons). Since the start of the 2017/18 winter influenza season in week 2, 460 outbreaks were recorded (as of February 14).
https://www.chp.gov.hk/files/pdf/fluexpress_week06_15_02_2018_eng.pdf
 In comparison, 225, 120 and 112 outbreaks were recorded in the same duration of surveillance (five complete weeks) in the 2014/15 winter, 2015/16 winter and 2017 summer seasons respectively, as compared with 438 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, 300 severe influenza cases among all ages have been reported, including 174 deaths (as of February 14).
https://www.chp.gov.hk/files/pdf/fluexpress_week06_15_02_2018_eng.pdf
 • Among the adult fatal cases, about 82% 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 14), 1.9% 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).
Global Situation of Influenza Activity
 
Influenza activity remained high in the temperate zone of the northern hemisphere while in the temperate zone of the southern hemisphere activity was at inter-seasonal levels. Worldwide, influenza A accounted still for the majority of influenza detections but influenza B (mostly from the Yamagata lineage) increased in recent weeks.
  • In Mainland China (week ending Feb 4, 2018), the influenza activity in both southern and northern provinces continued to decrease but still remained high. The proportion of influenza A detection continued to increase and 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 5.1 %, lower than that reported in the previous week (5.9%) but higher than that in the corresponding period in 2015-2017 (3.1%, 3.0%, 3.5%). In northern provinces, that proportion was 4.2%, lower than that reported in the previous week (4.8%) but higher than that in the corresponding period in 2015-2017 (3.0%, 3.8%, 3.5%). The proportion of influenza detections in the week ending February 4, 2018 was 40.4% (62.3% influenza A and 37.7% influenza B).
  • In Macau (week ending Feb 3, 2018), the influenza activity decreased but remained at high level. The proportions of ILI cases in emergency departments among adults and children decreased. The proportion of influenza detections was 36.4%, lower than 54.1% in the previous week.
  • In Taiwan (week ending Feb 10, 2018), influenza activity showed a decreasing trend, but was still at the peak of the season. In the week ending February 10, the proportion of ILI cases in emergency department was 13.15% which was above the threshold of 11.4%. The predominating virus was influenza B.
  • In Japan (week ending Feb 4, 2018), the influenza season has started in late November 2017. The average number of reported ILI cases per sentinel site increased to 54.33 in the week ending February 4, 2018 from 52.35 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) and A(H1N1)pdm09.