2007-2008年齐齐哈尔市流感监测结果分析

[目的]监测流感流行趋势,了解流感流行优势株。[方法]对齐齐哈尔市2007～2008年流感监测资料进行分析。[结果]2家哨点测医院2007年10月至2008年3月合计报告流感样病例2956例,占同期门急诊就诊病例总数75153例的3．93％。全市未发生流感暴发疫情,实验室收到并检测302份ILI标本,分离出19株流感病毒（分离率为6．29％）。其中,A（H1N1）亚型2株,A（H3N2）亚型10株,B型Yamagata系6株,B型Victoria系1株。[结论]2007～2008年度齐齐哈尔市流感呈散发状态,分离的流感毒株主要是H3N2和B／Yamagata。     

Influenza activity--United States and worldwide, 2007-08 season

During the 2007-08 influenza season, influenza activity peaked in mid-February in the United States and was associated with greater mortality and higher rates of hospitalization of children aged 0-4 years, compared with each of the previous three seasons. In the United States, influenza A (H1N1) was the predominant strain early in the season; influenza A (H3N2) viruses increased in circulation in January and predominated overall. While influenza A (H1N1), A (H3N2), and B viruses cocirculated worldwide, influenza A (H1N1) viruses were most commonly reported in Canada, Europe, and Africa, and influenza B viruses were predominant in most Asian countries. This report summarizes influenza activity in the United States and worldwide during the 2007-08 influenza season (September 30, 2007-May 17, 2008).     

Influenza season 2007/'08 in the Netherlands: antigenic variation, oseltamivir resistance and vaccine composition for the 2008/'09 season

The first signs of influenza activity during the 2007/'08 influenza season in the Netherlands were sporadic isolations of influenza viruses between week 40 and week 52 of 2007. The frequency of virus isolations and clinical influenza activity increased after week 1 of 2008 and peaked around week 9. In this week, 7.2 patients with influenza-like illness were recorded per 10,000 inhabitants. The influenza epidemic was caused primarily by influenza A/H1N1 viruses and influenza B viruses. Two antigenically distinct variants of influenza A/H1N1 viruses were isolated, which resembled the 2007/'08 vaccine reference strain A/Solomon Islands/3/06 and the new vaccine reference strain A/Brisbane/59/07, respectively. The most remarkable finding was that 27% of the A/H1N1 viruses isolated in the Netherlands during the 2007/'08 epidemic were resistant to the neuraminidase inhibitor oseltamivir. The isolated influenza B viruses originated from the B/Yamagata/16/88 lineage and did not match the vaccine strain, which originated from a different and antigenically distinct lineage of influenza B viruses (B/Victoria/2/87). Only a small number of influenza A/H3N2 viruses was isolated, which were related to the vaccine strain for this subtype (A/Wisconsin/67/05). Thus in contrast to previous influenza seasons, A/H3N2 viruses did not play a major role in the 2007/'08 influenza season in the Netherlands. For the 2008/'09 influenza season, the World Health Organization has recommended the following vaccine composition: A/Brisbane/59/07 (H1N1), A/Brisbane/10/07 (H3N2) and B/Florida/4/06.     

Influenza surveillance in Victoria, 2005

Influenza activity remained within normal seasonal activity with a well-defined peak at week 29 (beginning 18 July) during the Victorian influenza season from May to September 2005. Surveillance was based on sentinel general practice influenza-like illness (ILI) notifications with laboratory confirmation, medical locum service ILI notifications and laboratory notification of influenza detections. One thousand and eighty-seven consultations for ILI were reported from 38 general practices, while medical practitioners from the locum service reported 317 consultations for ILI. The average weekly rate of ILI from sentinel surveillance was 7.3 per 1,000 consultations. Similar numbers of influenza A subtypes H1N1 and H3N2 were detected; 45 per cent of which were A/California/7/2004-like (H3), 44 per cent were A/New Caledonia/20/99-like (H1) and 11 per cent were A/Wellington/1/2004 (H3). Of the influenza B samples, 67 per cent were B/Hong Kong/330/2001-like and 33 per cent were B/Shanghai/361/2002-like. The influenza vaccine for 2005 contained: A/New Caledonia/20/99(H1N1)-like virus, A/Wellington/ 1/2004(H3N2)-like virus, and B/Shanghai/361/2002-like virus. Although the predominant H3 and B circulating strains were not included in the vaccine, there was reasonable serological cross protection between vaccine and circulating strains.     

Epidemiological, clinical, and virological features of influenza outbreaks in Pune, India, 1980

During the course of continuous surveillance of influenza in 1980 in Pune, India, which has a tropical monsoon climate, three outbreaks of acute respiratory infection (ARI) were investigated in March (hot season), in July—September (rainy season), and in November (cold season); sporadic cases during the interepidemic months were also studied. The first outbreak was associated with influenza A virus (H3N2), the second with influenza A viruses (H3N2) and (H1N1) and influenza B virus, but fewer influenza viruses were isolated during the third outbreak. The illnesses affected all age groups including infants and adults over 60 years of age, although the paediatric age group was mainly affected. The ARI outbreaks associated with the hot and cold seasons commenced at about the time the weather changed whereas the mixed influenza A (H3N2) and A(H1N1) outbreaks occurred in the middle of the rainy season.     

广东省2005—2007年流行性感冒流行特征分析

目的分析广东省2005—2007年流感流行特征，为科学防治流感提供依据。方法对2005—2007年广东省流感监测系统的监测资料进行描述性流行病学分析，监测资料包括广东省13个地级市的14家城市综合医院或儿童医院、16所社区门诊部、16所中小学校和6家县级综合医院等的哨点医院收集门诊流感样病例（以下简称ILI）就诊信息；各地暴发疫情监测信息；来自哨点医院监测系统和暴发疫情收集的ILI标本的病原学监测资料。结果2005—2007年的哨点医院监测结果显示14家城市医院的流感样病例占门诊就诊人数百分比（以下简称ILI％）周平均为5．17％；3年中ILI％在3—7月达到高峰，而每年ILI％的高峰有所不同；2005年流感活动在3—5月有1个高峰，这个高峰是A型流感病毒（H3N2亚型）和A型流感病毒H1N1亚型共同引起的；2006年在3—4月和6月有2个流行高峰，这2个高峰分别是由B型流感病毒（Victoria系）和A型流感病毒（H1N1亚型）引起；而2007年只在6月有1个高峰，是由A型流感病毒（H3N2）引起。2005—2007年分别报告的ILI暴发疫情分别为121、172和40起，发病人数累计17310人，暴发疫情中的流感病毒毒株的流行和变化趋势与定点医院监测到的毒株流行和变化趋势一致。92％的暴发疫情发生在学校和托幼机构，而学校监测哨点的ILI％的高峰出现也较其他监测哨点医院要早1周。结论广东省流感流行的季节性高峰在春夏季，呈单峰或双峰型。中小学校和托幼机构是广东省流感防控的重点。     

上海地区某医院门诊儿童流感社会经济负担调查

目的 监测和评估2011年至2012年流感季节上海地区儿童流行性感冒(流感)的流行特征及其相应社会经济负担.方法 在2011年6月至2012年5月连续1年间,前瞻性监测因流感样疾病就诊于复旦大学附属儿科医院的门诊患儿,收集呼吸道标本和临床资料,进行流感病毒的检测.在流感暴发流行期间,采用问卷调查法评估确诊病例的疾病负担.结果 共入选1 119例患儿,流感病毒阳性病例370例(33.1％),甲型H3N2流感病毒阳性109例(9.7％),乙型流感病毒阳性279例(24.9％),未发现新型甲型H1N1流感病毒感染病例.不同月份流感检出率为1.1％ ～ 91.2％,不同月份优势流行株有所差异,2011年12月至2012年2月以乙型流感流行为主,2012年3月至2012年4月以甲型H3N2流感流行为主.共232例确诊流感的患儿接受问卷调查,其中甲型H3N2流感儿童病例69例,乙型流感儿童病例163例.每例流感患儿在医院就诊的平均费用为706.10元,每例流感患儿因家人误工造成的间接经济损失为293.80元,每例流感患儿总的平均费用为999.90元.每例平均就诊次数2.7次;抗生素使用率67.2％;家庭成员继发发病率21.1％;肺炎并发症发生率5.6％.甲型H3N2流感与乙型流感对于患儿及其家庭所造成的疾病负担无明显差异.结论 2011年6月至2012年5月期间上海地区儿童流感主要系甲型H3N2流感病毒和乙型流感病毒感染所致.在流感流行期间,流感对儿童及其家庭有明显的社会经济学影响,提倡接种流感疫苗预防儿童流感,降低疾病负担.     

2003年广东省流感病毒的流行概况及特征

目的了解2003年广东省流感病毒的流行特点和抗原变异情况。方法根据广东地区流感监测资料进行分析；用交叉血凝抑制试验检测病毒的抗原性；用逆转录-聚合酶链反应扩增病毒HA1基因，纯化产物进行核苷酸序列测定。将序列和Genebank中相关序列进行比较，用MegAlign软件绘制种系发生树。结果全年分离到510株流感病毒，其中H3N2亚型流感481株，占92．4％；乙型流感29株，占7．6％。实验室证实流感爆发52起，其中50起暴发是由H3N2亚型流感病毒引起，2起暴发是由乙型流感病毒引起。H3N2亚型流感病毒抗原性和疫苗侏A／Panama／2007／99（H3N2）有所不同。类似干A／Fujian／411／02（H3N2）。在HAl区氨基酸序列上，和疫苗株A／Panama／2007／99（H3N2）同源性为92．1％，存在有25个氨基酸差异。28株乙型流感病毒属于Victoria系，抗原性类似疫苗侏B／HongKong／330／01，1株乙型病毒属于Yamagata系，抗原性不同干B／sichuan／379／99。结论2003年广东省流感活动比2002年要强；同时流行着甲型（H3N2）和2个谱系的乙型流感病毒，H3N2亚型毒侏是优势侏，抗原性发生了漂移。     

Influenza activity in China: 1998-1999

During 1989-1999, influenza A H3N2 and H1N1 subtypes and B type viruses were still co-circulating in human population in China, while influenza A (H3N2) virus was predominant strain. The two antigenically and genetically distinguishable strains of influenza B virus were also still co-circulating in men in southern China. The antigenic analysis indicated that most of the H3N2 viruses were A/Panama/2007/99 (H3N2)-like strain, the most of the H1N1 viruses were antigenically similar to A/Beijing/262/95 (H1N1) virus. However, most of the influenza B viruses were B/Beijing/184/93-like strain, but few of them were antigenically similar to B/Shandong/7/97 virus. In the summer of 1998, the influenza outbreaks caused by H3N2 subtype of influenza A virus occurred widely in southern China. Afterwards, during 1998-1999 influenza season, a severe influenza epidemic caused by H3N2 virus emerged in northern China. The morbidity was reached as high as 10% in Beijing area. It was interesting that during influenza, surveillance from 1998 to 1999, five strains of avian influenza A (H9N2) virus were isolated from outpatients with influenza-like illness in July-August of 1998, and another one was repeatedly isolated from a child suffering from influenza-like disease in November of 1999 in Guangdong province. The genetic analysis revealed that the five strains isolated in 1998 were genetically closely related to H9N2 viruses being isolated from chickens (G9 lineage virus), whereas, A/Guangzhou/333/99 (H9N2) virus was a reassortant derived from reassortment between G9 and G1 lineage of avian influenza A (H9N2) viruses due to its genes encoding the HA, NA, NP and NS proteins, closely related to G9 lineage virus, the rest of the genes encoding the M and three polymerase (PB2, PB1 and PA) were closely related to G1 lineage strain of H9N2 virus. However, no avian influenza A (H5N1) virus has so far been isolated neither from in or outpatients with influenza-like disease in mainland China. Unfortunately, where did the reassortment occur and how did the reassortant transmit to men? These questions are still unknown.     

2009年南平市流感监测点病原监测结果分析

目的分析南平市流感监测点分离的流感毒株,探讨流行规律,为防治提供依据。方法选择南平市两所流感哨点监测医院,采集流感样病例（ILI）呼吸道咽拭子,利用MDCK细胞法分离病毒及用红细胞凝集抑制试验对病毒进行型和亚型的鉴定分析。结果 2009年采集流感样病例（ILI）样品1 848份,分离到240株流感病毒,分离率为13.0%。其中H1N1型流感病毒株85株,H3N2型流感病毒株42株,B型流感病毒株56株,新H1N1型流感病毒株57株。呈现5-9月和11-12月两个活动高峰。结论 2009年南平市流感病毒优势株在5-9月以A型（H1N1,H3N2）及B型（B-yamagata,B-victoria）共存。11-12月由优势株亚型逐渐过渡为A（新甲型H1N1）,少数样品检出B型（B-yamagata,B-victoria）流感。     

Annual report of the National Influenza Surveillance Scheme, 2005

Surveillance of influenza in Australia is based on laboratory isolation of influenza viruses, sentinel general-practitioner reports of influenza-like illness, and absenteeism data from a major national employer. In 2005, 4,575 cases of laboratory-confirmed influenza-like illness were reported, which was 115 per cent higher than in 2004. The influenza season started in the first week of June, with peak activity in early August, a month earlier than in 2004. Influenza A was the predominant type notified (73%), while influenza B activity continued to increase compared to previous years. During 2005, the influenza notification rate amongst persons aged over 65 years (22 cases per 100,000 population) was 70 per cent higher than the mean rate of the last four years. One thousand one hundred and seventy-four influenza isolates from Australia were antigenically analysed: 689 were A(H3N2), 210 were A(H1N1) strains and 275 were influenza B viruses. Continued antigenic drift was seen with the A(H3N2) viruses from the previous reference strains with approximately one quarter of isolates being distinguishable from A/Wellington/1/2004-like viruses and more closely matched to A/California/7/2004-like viruses.     

Update: Influenza activity--United States and worldwide, 2006-07 season, and composition of the 2007-08 influenza vaccine

During the 2006-07 season, influenza activity peaked in mid-February in the United States and was associated with less mortality and lower rates of pediatric hospitalizations than during the previous three seasons. In the United States, influenza A (H1) viruses predominated overall, but influenza A (H3) viruses were isolated more frequently than influenza A (H1) viruses late in the season. Although influenza A (H1), A (H3), and B viruses cocirculated worldwide, influenza A (H3) viruses were the most commonly reported type in Europe and Asia. Sporadic cases of avian influenza A (H5N1) virus infections associated with severe illness or death were reported among humans in Cambodia, China, Egypt, Indonesia, Laos, Nigeria, and Viet Nam. This report summarizes influenza activity in the United States and worldwide during the 2006-07 influenza season (October 1, 2006-May 19, 2007) and describes the composition of the 2007-08 influenza vaccine.     

The 2005-2006 influenza season in the Netherlands and the vaccine composition for the 2006-2007 season

The first sign of influenza activity in the Netherlands during the 2005-2006 influenza season was the isolation of influenza viruses in the last week of 2005. From Week 1 of 2006 onwards, an increase in clinical influenza activity was also observed that did not return to baseline levels until Week 15. Two waves of influenza activity were observed with peak incidences of 13.8 and 9.8 influenza-like illnesses per 10,000 inhabitants on Weeks 7 and 12, respectively. The first wave of influenza was caused primarily by influenza B viruses, whereas the second wave was caused predominantly by influenza A/H3N2 viruses. The influenza B viruses appeared to belong to two different phylogenetic lineages and were antigenically distinguishable from the vaccine strain. The isolated influenza A/H3N2 viruses were closely related to the vaccine strain for this subtype and only minor antigenic differences with the vaccine strain were observed for a limited number of isolates. Only a small number of influenza A/H1N1 viruses were isolated, which all closely resembled the H1N1 vaccine strain. For the 2006-2007 influenza season, the World Health Organization has recommended the following vaccine composition: A/Wisconsin/67/05 (H3N2), A/New Caledonia/20/99 (H1N1) and B/Malaysia/2506/05.     

Update: influenza activity--United States and worldwide, 2002-03 season,and composition of the 2003-04 influenza vaccine

In collaboration with the World Health Organization (WHO), its collaborating laboratories, state and local health departments, health-care providers, and vital statistic registries, CDC conducts surveillance to monitor influenza activity and to detect antigenic changes in the circulating strains of influenza viruses. During the 2002-03 influenza season, influenza A (H1), A (H3N2), and B viruses co-circulated in the Northern Hemisphere. Human infections with avian influenza A (H5N1) and A (H7N7) viruses were reported in Hong Kong and the Netherlands, respectively. In the United States, the 2002-03 influenza season was mild; influenza A (H1) and B viruses circulated widely, and the predominant virus varied by region and time of season. This report summarizes influenza activity in the United States and worldwide during the 2002-03 influenza season and describes the composition of the 2003-04 influenza vaccine.     

Surveillance for influenza--United States, 1994-95, 1995-96, and 1996-97 seasons.

PROBLEM/CONDITION: Influenza epidemics occur nearly every year during the winter months and are responsible for substantial morbidity and mortality in the United States, including an average of approximately 114,000 hospitalizations and 20,000 deaths per year. REPORTING PERIOD: This report summarizes U.S. influenza surveillance data from October 1994 through May 1997, from both active and passive surveillance systems. DESCRIPTION OF SYSTEM: During the period covered, CDC received weekly reports from October through May from a) state and territorial epidemiologists on estimates of local influenza activity, b) approximately 140 sentinel physicians on their total number of patient visits and the number of cases of influenza-like illness (ILI), and c) approximately 70 World Health Organization (WHO) collaborating laboratories in the United States on weekly influenza virus isolations. WHO collaborating laboratories also submitted influenza isolates to CDC for antigenic analysis. Throughout the year, vital statistics offices in 121 cities reported deaths related to pneumonia and influenza (P&I) weekly, providing a measure of the impact of influenza on mortality. RESULTS: During the 1994-95 influenza season, 25 state epidemiologists reported regional or widespread activity at the peak of the season. Cases of ILI reported by sentinel physicians exceeded baseline levels for 4 weeks, peaking at 5%. Influenza A(H3N2) was the most frequently isolated influenza virus type/subtype. The longest period of sustained excess mortality was 5 consecutive weeks, when the percentage of deaths attributed to P&I exceeded the epidemic threshold, peaking at 7.6%. During the 1995-96 season, 33 state epidemiologists reported regional or widespread activity at the peak of the season. ILI cases exceeded baseline levels for 5 weeks, peaking at 7%. Influenza A(H1N1) viruses predominated, although influenza A(H3N2) and influenza B viruses also were identified throughout the United States. P&I mortality exceeded the epidemic threshold for 6 consecutive weeks, peaking at 8.2%. The 1996-97 season was the most severe of the three seasons summarized in this report. Thirty-nine state epidemiologists reported regional or widespread activity at the peak of the season. ILI reports exceeded baseline levels for 5 consecutive weeks, peaking at 7%. The proportion of respiratory specimens positive for influenza peaked at 34%, with influenza A(H3N2) viruses predominating. Influenza B viruses were identified throughout the United States, but only one influenza A(H1N1) virus isolate was reported overall. The proportion of deaths attributed to P&I exceeded the epidemic threshold for 10 consecutive weeks, peaking at 9.1%. INTERPRETATION: Influenza A(H1N1), A(H3N2), and B viruses circulated during 1994-1997. Local surveillance data are important because of geographic and temporal differences in the circulation of influenza types/subtypes. PUBLIC HEALTH ACTIONS: CDC conducts active national surveillance annually from October through May for influenza to detect the emergence and spread of influenza virus variants and monitor the impact of influenza-related morbidity and mortality. Surveillance data are provided weekly throughout the influenza season to public health officials, WHO, and health-care providers and can be used to guide prevention and control activities, vaccine strain selection, and patient care.     

河北省2001～2006年度流感的实验室监测

目的：了解河北省2001—2006年度流感病毒的流行趋势及主导毒株的交替规律。方法：在流感流行季节，采集咽拭子标本用MDCK细胞培养分离流感病毒，经血凝抑制试验鉴定病毒型别。结果：2001年11月-2006年3月共分离到流感病毒281株，血清学鉴定结果A（H1N1）亚型58株，占20．64％，A（H3N2）亚型162株，占57．65％，B型61株，占21．71％。在2001—2002、2003—2004年流行期，以A（H3N2）亚型流感病毒占优势，2002—2003、2004—2005年流行期，为A（H3N2）亚型和B型同时流行，2005—2006年流行期，A（H1N1）、A（H3N2）亚型和B型同时流行。我省流感病毒流行高峰期一般在12月到次年的1月之间。结论：通过不同年份流感实验室监测结果的分析，对了解河北省流感流行特点、毒株亚型分布具有重要意义。     

Age distribution of patients with medically-attended illnesses caused by sequential variants of influenza A/H1N1: comparison to age-specific infection rates, 1978-1989

Since influenza A/H1N1 viruses reappeared during the 1977-1978 season, this subtype has contributed 27% of 6,609 documented influenza infections of persons with acute respiratory disease presenting to clinics serving as surveillance sites of the Influenza Research Center in Houston for the 12-year period ending June 1989. Wide differences in the distribution of H1N1 viruses occurred by age group: more than 50% of H1N1 infections were detected among persons aged 10-34 years, compared with 28% for influenza A/H3N2 and 35% for influenza B. Over age 35 years, the contribution of H1N1 viruses dropped to only 4%, compared with 20% and 16% for influenza A/H3N2 and influenza B, respectively. When birth dates of persons with positive cultures were examined, it was found that most of the H1N1-positive persons were born after 1950. Concurrently, longitudinal studies of families and other adults under intensive surveillance for infection, including cultures of all respiratory illnesses and tests for serum antibody rise over the respiratory disease season, revealed appreciable infection rates for adults born before 1950. Furthermore, the annual peak of hospitalization of older persons with pneumonia and other acute respiratory illnesses was significantly correlated with the peak of H1N1 virus activity in 1978-1979, a year when H1N1 viruses were the only influenza viruses prevalent. These observations indicate that many persons infected with influenza A/H1N1 viruses that circulated from 1946 through 1953 have immunity which has persisted for more than 25 years but this immunity is not complete. Reinfection that may result in serious illness in older vulnerable adults does occur but with lower frequency than with influenza A/H3N2 infection. Currently prevalent H1N1 variants are antigenically different from those that circulated in the 1950s; however, older adults readily acquire immunity to these new variants--perhaps as a result of immunologic priming that occurred in childhood.     

Influenza surveillance in Victoria, 2006

The Victorian influenza season in 2006 remained within normal seasonal activity thresholds and was relatively mild compared with recent years. The season peaked in mid-August, with influenza-like illness (ILI) rates from general practitioner sentinel surveillance and the Melbourne Medical Locum Service (MMLS), and cases of laboratory-confirmed influenza notified to the Department of Human Services, reaching their zeniths within one week of each other. A total of 74 general practitioners (GPs) participated in the sentinel surveillance in 2006, reporting a total of 136,732 consultations during the surveillance period from May to September inclusive. Participating GPs reported a total of 765 patients with an ILI; an average ILI rate of 5.6 cases per 1,000 consultations. The average ILI rate from the MMLS in the same period was 8.5 cases per 1,000 call-outs. Eighty-two per cent of laboratory-confirmed influenza notifications during the surveillance period were type A; the remainder were type B. Typing indicated circulation of two predominant strains during the season: A/Wisconsin/67/2005(H3N2)-like virus and B/Malaysia/2506/2004-like virus. The influenza vaccine for 2006 contained A/New Caledonia/20/ 99(H1N1)-like virus, A/California/7/2004(H3N2)-like virus and B/Malaysia/2506/2004-like virus.     

Communicable Diseases Network Australia National Arbovirus and Malaria Advisory Committee annual report, 2006-07

This report describes the epidemiology of mosquito-borne disease in Australia for the mosquito-borne disease season 1 July 2006 to 30 June 2007, which was moderately low compared to previous seasons. Ross River virus (RRV) infections (55%), Barmah Forest virus (BFV) infections (29%) and overseas acquired malaria (11%) were the most common mosquito-borne diseases reported in 2006-07. The number, proportion and rate of national BFV notifications were the second highest on record since 1998-99. The Northern Territory reported the highest BFV notification rate this season. BFV notification rates were the highest in the 40-59 year age groups when compared to other age groups. The number, proportion and rate of RRV notifications were moderately low this season compared with previous seasons. The highest RRV rate was reported by Western Australia from the Kimberley region. The highest age-specific RRV notification rate was observed in the 40-59 year age groups. Locally acquired dengue virus notifications were low this season compared to previous seasons, with a small outbreak of dengue serotype 3 in 39 cases confined to the greater Townsville region. There were 640 notifications of malaria in 2006-07 of which none were reported as locally acquired. This was the third highest number of malaria notifications since 2001. Plasmodium falciparum was reported as the infecting species in 47% of the malaria notifications and Plasmodium vivax for 40% of cases. Young adolescents and adults in the 15-29 year age group had the highest number of cases accounting for 32% of notifications. Sentinel chicken surveillance data for flaviviruses and sentinel pig surveillance data for Japanese encephalitis virus are also reported.     

Influenza season 1998/99; composition of vaccine for 1999/2000]

The first indication of influenza activity in the Netherlands in the 1998/'99 season was the isolation of an influenza B virus in week 47 of 1998. In subsequent weeks influenza activity slowly increased, reaching a peak in week 6 of 1999. After a gradual decline for three weeks a second peak was reached in week 8 of 1999. The first wave of influenza activity was primarily caused by influenza B viruses, whereas during the second wave predominantly influenza A viruses of the A/H3N2 subtype were isolated. The antigenic properties of the influenza A viruses resembled those of the viruses isolated in the previous season and the vaccine strain A/Sydney/5/97. The influenza B viruses did not completely match with B/Harbin/7/94 which is most commonly used for vaccine production. The vaccine, however, did provide good protection against the epidemic strains of influenza. This season influenza A/H1N1 viruses did not play a significant part and only a small number of viruses of this subtype were isolated at the end of the season. For the influenza season 1999/2000 it is recommended by the World Health Organization that the vaccines contain the following (or similar) virus strains: A/Sydney/5/97 (H3N2), A/Beijing/262/95 (H1N1) and B/Beijing/184/93.