Internet-based monitoring of influenza-like illness in the general population: Experience of five influenza seasons in the Netherlands

Like in most other countries, influenza surveillance in The Netherlands is based upon influenza-like illness (ILI) consultations reported by sentinel general practitioners (GP). In addition, an internet-based monitoring of ILI in the general population started in 2003/2004 (Great Influenza Survey (GIS)). We compared GIS results over 5 influenza seasons with results from the GP system. Weekly ILI incidence from GIS correlated well with ILI incidence from the GP system the same week and even better 1 week later. This suggests that GIS is useful for early detection of trends in influenza activity. However, two important vulnerable groups, children and the elderly, are clearly underrepresented in the GIS. Furthermore, virological confirmation is lacking in the GIS. So, GIS can be a useful addition to the GP system, especially when representativeness can be improved and when participation remains at the current high level.     

2013-2017年平顶山市流感监测分析

目的分析2013-2017年平顶山市流感流行特征,为流感防控措施的制定提供科学依据。方法通过中国流感监测信息系统,收集哨点医院流感样病例(ILI)报告情况,对符合采样要求的ILI采集鼻咽拭子,用realtime PCR方法检测流感病毒亚型,开展病原学监测。结果2013-2017年共上报ILI 35979例ILI,平均为2.88%;主要集中5岁以下儿童(50.61%);共采集ILI标本3299份,检出阳性标本575份,阳性率为17.43%;其中季节H3型占45.57%,B型占33.04%,新H1N1占21.22%。男女检出率差异无统计学意义;阳性标本主要集中在15岁以下儿童,特别是学生和幼托儿童。结论某市近几年流感流行处于较低水平,无明显高发趋势;在流行季节,季节性H3型,B型和新H1N1型交替出现,以季节性H3型为主;学生和托幼儿童防控流感暴发疫情的重点人群。     

2013 - 2018年度保定市流感监测分析

目的 分析保定市2013 - 2018年度流感监测资料,阐明流行特征,为制定流感防控措施提供科学依据。方法 收集中国流感监测信息系统中保定市哨点医院5个流行年度的流感样病例（ILI）、病原学、暴发疫情监测数据,进行描述性流行病学分析。结果 2013 - 2018年度保定市流感哨点医院共收集流感样病例数51 591例,就诊比例为2.81%,流感样病例中15岁以下儿童占83.37%。采集咽拭子标本8 586份,核酸阳性881份,阳性率为10.26%,H3N2亚型324份,甲型H1N1亚型292份,B型260份,混合型5份。5个监测年度共报告 ILI 聚集疫情 6 起,均发生在小学,1起为腺病毒感染引起,5起流感病毒感染引起的疫情病毒型别与当年流行的优势株一致。结论 2013 - 2018年度保定市流感高峰期出现在冬季;各年度流感病毒优势毒株轮流出现;流感样病例以15岁以下少年儿童为主,聚集疫情主要在小学发生,应加强中小学校等聚集性场所暴发疫情监测。     

A comparison of influenza and respiratory syncytial virus infections among infants admitted to hospital with acute respiratory infections.

Among 741 children under 5 years admitted to hospital with respiratory infections during two winters, infection with influenza A virus was diagnosed in 70 (9%), with influenza B virus in 8 (1%), and with respiratory syncytial virus (RSV) in 259 (35%). Both influenza virus and RSV infections were diagnosed most frequently in children under the age of one year, and diagnosed more frequently in males than females. Influenza illnesses were more severe in boys than girls. Both infections occurred more often, but were not more severe, in children from a conurbation than in those from 'rural' areas. Convulsions were the cause of 36% of admissions with influenza A infections, but were rare in RSV infections. Bronchiolitis was the reason for 39% of admissions with RSV infections, but was rare in influenza infections. It is suggested that infants admitted to hospital are a good source of influenza virus strains for monitoring antigenic variation.     

Effectiveness of trivalent and pandemic influenza vaccines in England and Wales 2008-2010: results from a cohort study in general practice

Estimation of influenza vaccine effectiveness (VE) is complicated by various degrees of mismatch between circulating and vaccine strains each season. We carried out a cohort study to estimate VE of trivalent (TIV) and pandemic influenza vaccines (PIV) in preventing various respiratory outcomes among general practice (GP) patients in England and Wales between 2008 and 2010. Dates of consultations for influenza-like illness (ILI), acute respiratory tract infection (ARTI), lower respiratory tract infection (LRTI) and nasopharyngeal swabs were obtained from the patient-level electronic records of the 100 practices enrolled in a national GP network. Dates of vaccination with TIV and PIV were also extracted. Confounders including age, time period and consultation frequency were adjusted for through Poisson regression models. In the winter of 2008/9, adjusted VE of TIV in preventing ILI was 22.3% (95% CI 13.5%, 30.2%). During the 2009/10 winter VE for PIV in preventing ILI was 21.0% (5.3%, 34.0%). The VE for PIV in preventing PCR-confirmed influenza A/H1N1 (2009) was 63.7% (-6.1%, 87.6%). TIV during the period of influenza circulation of 2008/9 and PIV in the winter of 2009/10 were effective in preventing GP consultations for ILI. The cohort study design could be used each season to estimate VE; however, residual confounding by indication could still present issues, despite adjustment for propensity to consult.     

Mortality in children from influenza and respiratory syncytial virus

STUDY OBJECTIVE: To quantify mortality attributable to influenza and respiratory syncytial virus (RSV) infection in children. DESIGN AND METHODS: Comparison of death rates (all cause and certified respiratory) in England over winters 1989/90 to 1999/00 during and outside influenza and RSV circulation periods. Virus active weeks were defined from clinical and virological surveillance data. Excess deaths associated with weeks of either influenza or RSV activity over virus non-active weeks were estimated in each winter for age groups 1-12 months, 1-4, 5-9, and 10-14 years. The estimate obtained was allotted to influenza and RSV in the proportion derived from independent separate calculations for each virus. MAIN RESULTS: Average winter respiratory deaths attributed to influenza in children 1 month-14 years were 22 and to RSV 28; and all cause deaths to influenza 78 and to RSV 79. All cause RSV attributed deaths in infants 1-12 months exceeded those for influenza every year except 1989/90; the average RSV and influenza attributed death rates were 8.4 and 6.7 per 100 000 population respectively. Corresponding rates for children 1-4 years were 0.9 and 0.8 and for older children all rates were 0.2 or less, except for an influenza rate of 0.4 in children 10-14 years. CONCLUSIONS: Influenza and RSV account for similar numbers of deaths in children. The impact varies by winter and between age groups and is considerably underestimated if analysis is restricted to respiratory certified deaths. Summing the impact over the 11 winters studied, compared with influenza RSV is associated with more deaths in infants less than 12 months, almost equal numbers in children 1-4 years, and fewer in older children. Improved information systems are needed to investigate paediatric deaths.     

Influenza surveillance in Victoria, 2004.

Influenza activity during the traditional Victorian influenza season from May to October 2004 was low with no well-defined peak. Surveillance was based on sentinel general practice influenza-like illness (ILI) notification with laboratory confirmation, locum service ILI notification and laboratory reporting of influenza detections. Eight hundred and fifteen consultations for ILI were reported from 38 general practices and 216 consultations for ILI were reported from the locum service. The average weekly rate of influenza-like-illness from sentinel surveillance was 5.4 cases per 1,000 consultations, representing normal seasonal activity. Influenza A (H3N2) was the predominant circulating sub-type, 88 per cent of which were identified as A/Fujian/411/2002-like and 12 per cent as A/Wellington/1/2004. All influenza B was B/Shanghai/361/2002-like. There was some mismatch with the 2004 influenza vaccine, which contained A/New Caledonia/20/99(H1N1)-like virus, A/Fujian/411/2002(H3N2)-like virus, and B/Hong Kong/330/2001-like virus.     

Influenza surveillance in Korea: establishment and first results of an epidemiological and virological surveillance scheme

Surveillance is an important component of influenza control. This report describes the establishment and first results of the Korean Influenza Surveillance Scheme (KISS), an integrated clinical and laboratory surveillance network involving 622 public health centres (PHCs) and private clinics. Sentinel physicians reported cases of influenza-like illness (ILI) weekly and forwarded specimens for virus isolation and characterization. Influenza activity during the opening 2000-2001 season was milder and delayed compared with previous years. The ILI consultation rate corresponded well with the number of influenza virus isolates, both peaking in week 10 of 2001. Influenza A(H3N2) was the dominant isolate. The peak ILI consultation rate was higher in private clinics than in PHCs (5.04 vs 1.79 cases/1000 visits). An evaluation questionnaire generated potential enhancements to the scheme. KISS appears to represent the pattern of influenza activity accurately and will have a valuable role in monitoring and preventing epidemics in Korea.     

The effectiveness of influenza vaccination among nursery school children in China during the 2016/17 influenza season

BackgroundThe effectiveness of influenza vaccine among nursery school children has not been systematically studied. We conducted a cohort study of children from 13 nursery schools in Suzhou, China, to estimate the effectiveness of influenza vaccine against laboratory-confirmed influenza during 2016–17.MethodsChildren aged 36–72 months were chosen from 13 nursery schools from 3 District in Suzhou. The surveillance started 2 weeks after vaccination during October 2016–February 2017. Class teachers reported the names of students with ILI (influenza-like illness) to study clinicians on each school day. Further, local physicians collected the student’s nasopharyngeal swab or throat swab, either at a study clinic or at the child’s home. The swabs were sent to the National Influenza Network Laboratory in Suzhou Center for Disease Control and Prevention for influenza testing by RT-PCR.ResultA total of 4614 children were enrolled, of which 15 children (vaccinated: 2; unvaccinated: 13) were lost to follow-up. Of the remaining 4599 children, 558 swabs were collected. Among these swabs, 70 samples tested positive for influenza virus; 17 in the vaccinated group (B Victoria: 2; H3N2: 15) and 53 in the unvaccinated group (B Victoria: 14; A(H1N1)pdm09: 1; H3N2: 38). The overall influenza vaccine effectiveness (VE) during the influenza season of 2016–2017 was 20.6%. The incidence of developing ILI symptoms and healthcare seeking behavior through clinical visits was significantly lower in vaccinated children than in the unvaccinated group.ConclusionInfluenza vaccine protection in vaccinated and unvaccinated children showed no statistical difference and the VE percentage varied for different virus subtypes. However, the incidence rate of developing ILI and healthcare seeking behavior was significant lower in the vaccinated group than in the unvaccinated children. Larger studies are required to estimate the VE according to the influenza type, subtype, and lineage during influenza seasons in China in the future.     

Long time trends in influenza-like illness and associated determinants in The Netherlands

We analysed long-term epidemiological trends in influenza-like illness (ILI) in The Netherlands and used an ecological analysis to estimate its relationship with age, influenza vaccination, and virological aspects. This study used data from weekly ILI consultation reports from sentinel general practitioners (1986/1987 to 2006/2007), virological data from sentinel ILI patients (1992/1993 to 2006/2007), and data for influenza vaccine uptake (1991-2005). The incidence of ILI consultations, although varying during the study period, was estimated to decrease in the total population by 12.2/10 000 persons each season (95% CI 8.6-15.9). Uptake of influenza vaccination in people aged > or = 65 years (elderly) increased from 28% in 1991 to >70% since 1997. ILI incidence in the elderly declined by 1.7/10 000 persons (P=0.05) per percentage vaccine uptake per season. The decline in ILI incidence over the last 20 years could be related to the increased vaccine uptake. However, insufficient data were present to assess the impact of other potential contributing factors, such as diminished fitness of influenza viruses and changes in consulting behaviour.     

Self-reported prevalence of warts in children and GP consultation

Objective: Respiratory infections are a frequent causes of medical attendance. Influenza viruses increases this phenomena. The aim of this study was to prospectively identify GPs’ increased work in terms of visits and time. Methods: Over a period of five months 5 GPs recorded sex, age, number and place of visits, telephone consultations of the patients visited for acute respiratory disease (ARD)which included acute respiratory infections (ARI), influenza (FLU) and Influenza-like illness (ILI). Upper respiratory tract infections (URTI) were classified as sinusitis, rhinitis, otitis, tonsillitis, pharyngitis, laryngitis, Lower respiratory tract infections (LRTI) were classified as tracheitis, bronchitis, pneumonia, bronchopneumonia, acute episodes of chronic obstructive pulmonary disease (COPD) and asthma. FLU and ILI were considered two different entities on the basis of symptoms. Results: Acute respiratory disease increase of 22 patients attending every GP's office monthly (from 176 to 198 total visits). 6542 patients were observed. The incidence of ARD was 33.5% (2191: 1091 female and 1100 males). URTI affected 944 patients, LRTI 739, FLU 328 and ILI 180. The increase in home visits grew from 10 to 36. Each home visit took from 15 to 45 minutes. In a high number of cases (236), home visits were necessary for sick-leave certificates. FLU (54%) and LRTI (37.5%) required more attention, and they were the primary causes for visits. Telephone consultations took place for all ILI or FLU of minor severity and in young people.

Conclusion: During the winter there is an increased work-load for GPs due to the diffusion of influenza virus and respiratory tract diseases. “Burn out syndrome” is increasing among the GPs. Territorial GPs’ action is highly efficacious. Patients self-certification should be evaluated. Vaccine therapy could be more effective if done on a larger population. More research is needed.     

湖北省荆州市2010－2012年实验室确诊流感住院率估计

目的 估算2010－2012年湖北省荆州市流感所致严重急性呼吸道感染(SARI)病例的住院率。方法 2010－2012年在湖北省荆州市4家医院的住院病例中开展SARI监测,在患者知情同意后纳入收集人口学、临床表现、治疗情况及转归等信息,并采集呼吸道标本进行流感病毒PCR核酸检测。结果 2010年4月至2012年9月共纳入19 679例SARI病例,为荆州市城区常住居民,其中18 412例(93.6%)采集了鼻咽拭子开展PCR检测,阳性率为13.3%。实验室确诊流感导致的SARI住院率在2010－2012年连续3年的流感季分别为102/10万、132/10万和244/10万。不同的型别/亚型的流感病毒所致的住院率在2010－2011流感季 A(H3N2)为48/10万,A(H1N1)pdm2009为30/10万,B型为24/10万;2011－2012流感季A(H3N2)为42/10万,B型为90/10万;2012年4－9月A(H3N2)为 90/10万,B型为1/10万。A型和B型流感病毒所致住院均主要发生在<5岁年龄组,以0.5～岁组最高。结论 湖北省荆州市流感造成一定住院负担,不同型别/亚型流感在不同流感季会导致不同的住院率,应将<5岁儿童作为流感疫苗接种的重点推荐人群。     

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.     

陕西省2005—2009年流行性感冒监测分析

目的分析探讨2005—2009年陕西省流行性感冒(简称流感)流行特征,为流感的防控提供科学依据。方法收集陕西省2005—2009年4家流感监测哨点医院的流感样病例监测资料和流感病原学监测资料,分析流感样病例(ILI)占门诊病例的百分比的变化规律以及流感病毒各亚型的活动规律。结果陕西省2005—2009年各年的ILI%高峰出现在每年的12月份～次年的1月份,ILI主要集中在15岁以下儿童;2005—2009年度共检测ILI标本2760份,阳性548份;各年度流感流行的优势株均不相同,2005—2006年度为H1N1、H3N2混合流行,2006—2007年度优势株为B型的Victoria系,2007—2008年度为H3N2、Yamagata系混合流行,2008—2009年优势株为H1N1;流感病毒阳性的高峰时间主要集中在12月～次年的1月;流感病毒阳性主要分布在5～15岁和15～25岁年龄组。结论陕西省流感的活动规律较为明显,存在着一定的季节性,流行高峰为每年冬、春两季。2005—2009年陕西省流感的活动较为平稳,流行优势毒株不断发生变化。     

天津市河东区国家级流行性感冒监测点监测结果分析

目的分析天津市河东区2007-2008年度流行性感冒（下称流感）的病原学及流行特征。方法在流行季节每日对该区流感样病例（ILI）进行登记,并对部分病例采集咽拭子标本送至国家级流感检测实验室检测。结果2007年10月-2008年3月的26周,ILT共就诊22986人次,占门诊总量的10.28％。10岁以下学生、儿童是ILT的高发人群。共采集咽拭子标本157份,检出流感病毒80株,检出率为51％。按时间检出的不同型流感病毒株顺序规律为：乙型流感病毒（Yamagata）→乙型流感病毒（Victoria）→甲3型流感病毒→甲1型流感病毒。河东区流感流行有明显的季节性,即冬季为流感流行季节,流感高发时间在12月或次年的1月。结论ILI流行病学及病原学监测结果对于了解河东区流感流行特点,为制订流感防制策略提供及时准确的科学依据具有重要意义。     

中国2001～2003年流行性感冒流行特征分析

目的 分析中国2001～2003年流行性感冒(流感)流行特征。方法 收集2001～2003年全国流感监测网流感样病例(ILI)监测资料,流感病毒分离与鉴定结果以及爆发疫情信息进行分析。结果 2001～2003年,中国北方地区流感流行高峰为12月或次年1月,南方地区则为4、5、7、8月和11、12月。北方、南方地区ILI就诊百分比基线值分别为13.68％、13.08％。ILI的年龄构成与流感流行季节类型有关。流感爆发疫情以5月份最多(32％),一般在6月前后流感疫情毒株类型发生改变。结论 中国南、北方流感流行特征有所不同。南方地区可能存在春季流行高峰,尚需进一步监测和分析。南方地区4～6月期间流感爆发的毒株类型变化值得关注。     

Surveillance of respiratory virus infections in adult hospital admissions using rapid methods

Both influenza and respiratory syncytial virus (RSV) cause epidemics of respiratory illness of variable severity during the winter season. Influenza in particular has been blamed for hospital winter bed pressures, although it is thought that RSV may also play a role. Human metapneumovirus (hMPV) is a new respiratory virus reported to be important in children; only a limited number of studies are available for adult populations. We aimed to determine initially the burden of virologically confirmed infections, i.e. influenza, RSV and hMPV using polymerase chain reaction (PCR) technology and, in addition, to assess the feasibility of this approach as a surveillance tool for these respiratory viruses. Adult patients admitted to hospital in the previous 24 hours with onset of acute respiratory symptoms in the last 14 days were asked to participate. Informed written consent was obtained and nose and throat swabs taken. Multiplex PCR for influenza A (H1N1 and H3N2), influenza B and RSV A and B were carried out together with a separate PCR for hMPV. A total of 219 patients in 2001-2002 and 216 in 2002-2003 were tested and the combined results for both seasons were: 8 positive for influenza A/H1N1, 14 for influenza A/H3N2, 2 for influenza B, 14 for RSV A and 6 for RSV B. Most patients (261/435) were >65 years and most positives (30/44) were found within this age group. A number of patients aged >65 years who were positive for influenza (12/15) reported having had vaccine. In total, 373 samples were tested for hMPV and 20 were found positive across all age groups except the 45-54 years age group. As influenza activity was low during the study period the impact of infection on admissions could not be assessed. Nevertheless the viruses studied accounted for 15% of hospital admissions for respiratory infection. Most patients were aged >65 years, as expected. In the two years studied RSV and hMPV were each responsible for as many hospitalized cases of respiratory infection as influenza. Influenza infection must be considered even in those who give a history of vaccination. The molecular methods used in this study showed that surveillance of these respiratory viruses can be conducted and may help in the management of patients.     

Higher than expected seasonal influenza activity in Victoria, 2007

In 2007, the Victorian influenza season exceeded normal seasonal activity thresholds. The average rate of influenza-like illness (ILI) reported by general practitioners (GPs) participating in sentinel surveillance was 9.0 cases per 1,000 consultations, peaking at 22 cases per 1,000 consultations in mid-August. The average ILI rate reported by the Melbourne Medical Locum Service (MMLS) was 11.5 per 1,000 consultations over the season. The MMLS ILI rate peaked at 30 per 1,000 consultations at the same time as peak rates were reported by GPs, with a secondary peak observed three weeks later (22 cases per 1,000 consultations). Influenza cases notified to the Victorian Department of Human Services peaked in mid-August with a secondary peak of influenza A in early September. Of the influenza positive swabs collected by GPs and among those collected throughout the state, 92% were type A and 8% were type B. The most common strains identified in Victoria in the 2007 influenza season were A/ Brisbane/10/2007-like followed by A/Solomon Islands/3/2006-like. While neither virus strain was specifically included in the 2007 Australian influenza vaccine, reasonable cross protection was afforded by the strains in the vaccine.     

Prevalence and Seasonality of Influenza-like Illness in Children, Nicaragua, 2005�C2007

Although information about seasonality and prevalence of influenza is crucial for development of effective prevention and control strategies, limited data exist on the epidemiology of influenza in tropical countries. To better understand influenza in Nicaragua, we performed a prospective 2-year cohort study of influenza-like illness (ILI) involving 4,276 children, 2–11 years of age, in Managua, during April 2005–April 2007. One peak of ILI activity occurred during 2005, in June–July; 2 peaks occurred during 2006, in June–July and November–December. The rate of ILI was 34.8/100 person-years. A household risk factor survey administered to a subset (61%) of participants identified the following risk factors: young age, asthma, and increasing person density in the household. Influenza virus circulation was confirmed during each ILI peak by laboratory testing of a subset of samples. Our findings demonstrate a high rate of ILI, with seasonal peaks, in children in Nicaragua.