Chan, CP

CHEUNG, PHH

Jin, D

Emerging Microbes & Infections

Emerging Microbes & Infections (2017) 6, e78; doi:10.1038/emi.2017.76; published online 6 September 201

Pak-Hin Hinson Cheung

Chi-Ping Chan

Dong-Yan Jin

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To announce or not to announce: What is known about the 2016–2017 influenza season in Hong Kong?

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Title To announce or not to announce: What is known about the2016–2017 influenza season in Hong Kong?Author(s) CHEUNG, PHH; Chan, CP; Jin, DCitation Emerging Microbes & Infections, 2017, v. 6, p. e78Issued Date 2017URL http://hdl.handle.net/10722/248335Rights This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.OPENNEWS AND VIEWSTo announce or not to announce: What is known aboutthe 2016–2017 inﬂuenza season in Hong Kong?Pak-Hin Hinson Cheung, Chi-Ping Chan and Dong-Yan JinEmerging Microbes & Infections (2017) 6, e78; doi:10.1038/emi.2017.76; published online 6 September 2017The death toll of seasonal inﬂuenza in Hong Kong in 2017 has hit theheadlines and received broad media coverage worldwide. Somecommentators compared it with that of severe acute respiratorysyndrome (SARS) during the outbreak in 2003. What was it reallylike? As of 26 August 2017, the inﬂuenza activity in Hong Kong hadfurther declined from the peak and returned to the baseline, indicatingthat the 2016–2017 inﬂuenza season is over. From 5 May to 26August, 586 severe seasonal inﬂuenza cases were recorded, including19 pediatric cases (aged below 18). Among them, 429 adults and 3children had died. Hospitalization rates were high, especially for theelderly (aged ⩾ 65). H3N2 was the predominating subtype detected.It is known that H3N2 is more virulent than other subtypes such asH1N1,1 causing more severe infection and higher death rate. Itremains to be validated whether the predominant H3N2 viruses inthis season have undergone antigenic drifts that reduce vaccineeffectiveness, as seen in the 2014–2015 season. It is noteworthy thatmore than 35% of the H3N2 viruses found in May 2017 in HongKong contain N121K mutation in the hemagglutinin (HA) protein,which could render the vaccine less effective.2 To what extent thismight have exacerbated the severity of this inﬂuenza season in HongKong merits further investigations. Since 45.4% of the fatal cases areknown to have received the inﬂuenza vaccine for the 2016–2017season, the possibility that vaccination cannot effectively protectinfection with the circulating H3N2 viruses cannot be excluded.How does this season compare to the previous ones? The mostrecent H3N2 season was 2014–2015, whereas H1N1 predominated in2013–2014 and 2015–2016. Whereas seasonal inﬂuenza activity peakedin February and March in the previous three seasons, with anexceptional second wave seen in June 2015, it plateaued in July2017. Consistent with the notion that H3N2 is more virulent, therewere more severe cases and deaths in 2014–2015 than in 2013–2014 or2015–2016. In contrast, the numbers of severe and death cases in thepeak week were similar for 2014–2015 and 2016–2017. The 2016–2017season is drawing to a close at the end of August; the total number ofsevere and death cases does not exceed that of 2014–2015 (Table 1).The case fatality was about 2% in both seasons.The above statistics indicates that the 2016–2017 inﬂuenza season inHong Kong is not more severe than any previous H3N2 season, suchas the one in 2014–2015. This was further corroborated by tabulationof the numbers of severe cases by age groups, which indicated a similarpattern for the 2014–2015 and 2016–2017 seasons, in which peopleaged 50–64 and ⩾ 65 were most severely affected (Table 1). Underlyingdiseases and immunosuppression are common in the severe cases inthese age groups. The pattern was not seen for the two H1N1 seasonsin 2013–2014 and 2015–2016.Furthermore, the rates for inﬂuenza-associated hospitalization,severe cases and deaths in the 2016–2017 season in Hong Kong weregenerally within the boundaries expected for a H3N2 season andcomparable to those in other countries and regions in this andprevious H3N2 seasons. The disease burden of seasonal inﬂuenza issubstantial. As estimated by the Centers for Disease Control andPrevention (CDC), there might have been 9.2–35.6 million cases ofinﬂuenza-related illnesses, 140 000–710 000 hospitalizations and12 000–56 000 deaths annually in the United States since 2010. Forexample, in the H3N2-dominant 2003–2004 season, the estimatednumber of inﬂuenza-associated deaths with underlying respiratory andcirculatory causes in the United States was 48 614.3 The advancedinﬂuenza surveillance system in Hong Kong has just provided a real-life example in support of the estimation made by the CDC.The Center for Health Protection of Hong Kong has done a superbjob in providing near real-time monitoring of seasonal inﬂuenzaactivity in the territory. Starting from the 2014–2015 season, they wentone step further to announce their ﬁndings, including the numbers ofsevere seasonal inﬂuenza cases and deaths to the general public. Thisreal-time weekly update of inﬂuenza activity helps to increase theawareness and vigilance of people against the risk. However, it has alsotriggered extensive media coverage, including exaggerated descriptionand unfair comparison, which cause panic, anxiety and overreactionfrom residents, visitors and people from other regions.Inﬂuenza-associated excess deaths with underlying diseases aredifﬁcult to track and might not be detected timely by the inﬂuenzasurveillance system in adjacent regions. Hence, a comparison ofnumbers between different regions cannot reﬂect the severity ofseasonal inﬂuenza activity. Human infection of avian H5N1 andH7N9 viruses has a case fatality of 60% and 40%, respectively.Likewise, about of 10% of cases with SARS and 30% of cases withMiddle East respiratory syndrome are fatal. These are emerging viralpathogens with unusual properties. If seasonal inﬂuenza is a knownevil, they are unknown beasts. Direct comparison of the numbers ofSchool of Biomedical Sciences, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong, ChinaCorrespondence: D-Y JinE-mail: dyjin@hku.hkReceived 24 August 2017; accepted 25 August 2017Emerging Microbes & Infections (2017) 6, e78; doi:10.1038/emi.2017.76www.nature.com/emideaths caused by seasonal inﬂuenza and these emerging viruses istherefore misleading.Increasing the transparency of inﬂuenza surveillance and sharingmore information about seasonal inﬂuenza activity with the publicshould not be discouraged. In other words, not to announce is not anoption, but the question is how to explain to all stakeholders andeducate them about seasonal inﬂuenza, emerging microbes andinfections. There is much room for improvement in this aspect.The numbers of severe inﬂuenza cases and deaths in the 2016–2017season in Hong Kong remind us of the signiﬁcant morbidity andmortality caused by seasonal inﬂuenza. Reducing the disease burdenand the impact on public hospitals in Hong Kong is our nextchallenge. The percentage of people in the high-risk groups, includingchildren, the elderly and health professionals, in Hong Kong whoreceive inﬂuenza vaccination is relatively low. Providing moreincentives, including more attractive subsidizing schemes, to thesegroups might be helpful. Prescribing Tamiﬂu to the elderly who are athigher risk has also been shown to be a safe and effective prophylacticmeasure. Earlier concerns about the possibility that exposing morepeople to Tamiﬂu might accelerate the development of drug resistancecan be relieved.4 Nevertheless, seasonal inﬂuenza will still keep us busyin the years to come. New types of vaccines and antivirals are requiredin our battle against inﬂuenza viruses.1 Wright PF, Thompson J, Karzon DT. Differing virulence of H1N1 and H3N2 inﬂuenzastrains. Am J Epidemiol 1980; 112: 814–819.2 Trebbien R, Fischer TK, Krause TG et al. Changes in genetically drifted H3N2 inﬂuenzaA viruses and vaccine effectiveness in adults 65 years and older during the 2016/17season in Denmark. J Clin Virol 2017; 94: 1–7.3 Centers for Disease Control and Prevention (CDC). Estimates of deaths associated withseasonal inﬂuenza—United States, 1976–2007. MMWR Morb Mortal Wkly Rep 2010;59: 1057–1062.4 Gubareva LV, Besselaar TG, Daniels RS et al. Global update on the susceptibility ofhuman inﬂuenza viruses to neuraminidase inhibitors, 2015–2016. Antiviral Res 2017;146: 12–20.This work is licensed under a Creative Commons Attribution 4.0International License. The images or other third party material in thisarticle are included in the article’s Creative Commons license, unless indicated otherwisein the credit line; if thematerial isnot includedunder theCreativeCommons license,userswill need toobtainpermission fromthe licenseholder to reproduce thematerial. Toviewacopy of this license, visit http://creativecommons.org/licenses/by/4.0/r The Author(s) 2017Table 1 The number of severe inﬂuenza cases in recent seasons in Hong KongInﬂuenza season(number of weeks under study)PredominantsubtypeNumber of severe casesin the peak weekNumber of severe cases in the season by agegroup (years) Number of deaths inthe peak weekNumber of deathsin the season0 –17 18–49 50–64 65 or above Total2013−2014 (17) A/H1N1 32 23 54 73 139 289 22 1382014−2015 (17) A/H3N2 74 18 21 65 561 665 56 4472015−2016 (17) A/H1N1 44 27 58 133 218 436 18 1572016−2017 (17) A/H3N2 75 19 27 89 451 586 56 300Number of deaths includes deaths in public hospitals only. Original data: http://www.chp.gov.hk/ﬁles/xls/ﬂux_data.xlsx.The 2016–2017 inﬂuenza season in Hong KongP-HH Cheung et al2Emerging Microbes & Infections

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To announce or not to announce: What is known about the 2016–2017 influenza season in Hong Kong?

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