Epidemiological surveillance activities during the 2009 influenza pandemic in Spain: lessons learnt one year after

In this article the actions taken in the area of epidemiological surveillance in Spain during the influenza pandemic and the recommendations drawn from them during the progression of the pandemic are reviewed. The performance of the Surveillance Subcommittee established in the National Influenza Preparedness and Response Plan was central to the coordination of these activities. The Surveillance Subcommittee was immediately activated when the alert was issued. Its role is also described in this review. The existence of a National Plan allowed a rapid and coordinated response after the alert declaration. The epidemiological and virological surveillance of the influenza pandemic was adapted to an evolving situation. In addition to routine influenza monitoring systems, new surveillance systems were put in place such as a case-based surveillance for community influenza cases and a case-based surveillance for severe cases and deaths due to the pandemic. Among the lessons learned from this pandemic, we would highlight the need to strengthen the timely analysis of data collected during an alert, the need to promote the exchange of information among public health and health care professionals, and to strengthen the response capacity in order to have resilient and consolidated public health structures for future health alerts.     

Performance of public health surveillance systems during the influenza A(H1N1) pandemic in the Americas: testing a new method based on Benford's Law

The A(H1N1) influenza pandemic has been a challenge for public health surveillance systems in all countries. An objective evaluation has not been conducted, as yet, of the performance of those systems during the pandemic. This paper presents an algorithm based on Benford's Law and the mortality ratio in order to evaluate the quality of the data and the sensitivity of surveillance systems. It analyses records of confirmed cases reported to the Pan American Health Organization by its 35 member countries between epidemiological weeks 13 and 47 in 2009. Seventeen countries did not fulfil Benford's Law, and mortality exceeded the regional average in 40% of the countries. The results suggest uneven performance by surveillance systems in the different countries, with the most frequent problem being low diagnostic coverage. Benford's Law proved to be a useful tool for the evaluation of a public health surveillance system's performance.     

United States Centers for Disease Control and Prevention support for influenza surveillance, 2013–2021

ObjectiveTo assess the stability of improvements in global respiratory virus surveillance in countries supported by the United States Centers for Disease Control and Prevention (CDC) after reductions in CDC funding and with the stress of the coronavirus disease 2019 (COVID-19) pandemic.MethodsWe assessed whether national influenza surveillance systems of CDC-funded countries: (i) continued to analyse as many specimens between 2013 and 2021; (ii) participated in activities of the World Health Organization’s (WHO) Global Influenza Surveillance and Response System; (iii) tested enough specimens to detect rare events or signals of unusual activity; and (iv) demonstrated stability before and during the COVID-19 pandemic. We used CDC budget records and data from the WHO Global Influenza Surveillance and Response System.FindingsWhile CDC reduced per-country influenza funding by about 75% over 10 years, the number of specimens tested annually remained stable (mean 2261). Reporting varied substantially by country and transmission zone. Countries funded by CDC accounted for 71% (range 61–75%) of specimens included in WHO consultations on the composition of influenza virus vaccines. In 2019, only eight of the 17 transmission zones sent enough specimens to WHO collaborating centres before the vaccine composition meeting to reliably identify antigenic variants.ConclusionGreat progress has been made in the global understanding of influenza trends and seasonality. To optimize surveillance to identify atypical influenza viruses, and to integrate molecular testing, sequencing and reporting of severe acute respiratory syndrome coronavirus 2 into existing systems, funding must continue to support these efforts.     

Event-based internet biosurveillance: relation to epidemiological observation

ABSTRACT: BACKGROUND: The World Health Organization (WHO) collects and publishes surveillance data and statistics for select diseases, but traditional methods of gathering such data are time and labor intensive. Event-based biosurveillance, which utilizes a variety of Internet sources, complements traditional surveillance. In this study we assess the reliability of Internet biosurveillance and evaluate disease-specific alert criteria against epidemiological data. METHODS: We reviewed and compared WHO epidemiological data and Argus biosurveillance system data for pandemic (H1N1) 2009 (April 2009 - January 2010) from 8 regions and 122 countries to: identify reliable alert criteria among 15 Argus-defined categories; determine the degree of data correlation for disease progression; and assess timeliness of Internet information. RESULTS: Argus generated a total of 1,580 unique alerts; 5 alert categories generated statistically significant (p < 0.05) correlations with WHO case count data; the sum of these 5 categories was highly correlated with WHO case data (r=0.81, p<0.0001), with expected differences observed among the 8 regions. Argus reported first confirmed cases on the same day as WHO for 21 of the first 64 countries reporting cases, and 1 to 16 days (average 1.5 days) ahead of WHO for 42 of those countries. CONCLUSION: Confirmed pandemic (H1N1) 2009 cases collected by Argus and WHO methods returned consistent results and confirmed the reliability and timeliness of Internet information. Disease-specific alert criteria provide situational awareness and may serve as proxy indicators to event progression and escalation in lieu of traditional surveillance data; alerts may identify early-warning indicators to another pandemic, preparing the public health community for disease events.     

2009年广东省甲型H1N1流感流行特征分析

目的分析2009年广东省甲型H1N1流感大流行的流行特征,为采取相应的防控措施提供科学依据。方法收集中国疾病监测信息报告管理系统及广东省流感监测系统的流感样病例监测、病原学监测及暴发疫情监测数据,采用描述性流行病学方法分析2009年广东省甲型H1N1流感的流行特征,并用流感监测数据来估算广东省2009年到医院就诊者中的甲型H1N1流感病例数。结果2009年5月18日广东省报告首例甲型H1N1流感病例,截止2009年12月31日共有21个地级市累计报告甲型H1N1流感确诊病例9 784例,其中重症病例346例,危重病例141例,死亡36例;每周报告甲型H1N1流感病例数占全年病例总数的构成比高峰与流感监测的甲型H1N1流感就诊指数高峰相一致,均出现在2009年11月,并在12月回落,且流感样病例就诊指数也降至警戒线(5%)以下,与季节性流感高峰(7月)完全不同。从病例输入到社区传播可划分为:以国外病例输入为主的输入散发期(5月18日至6月17日);出现聚集性病例,病例主要局限于珠江三角洲的有限传播期(6月18日至7月30日);在全省流感监测网络中连续检出甲型H1N1流感核酸阳性病例为特征的持续传播期(7月31日至8月31日);病例以学校暴发为特征并在全省各市蔓延的广泛传播期(9月1日至12月31日)。分析834例临床资料完整的病例的临床表现主要以发热(95.56%)、咳嗽(59.11%)、咽痛(42.45%)等呼吸道症状为主。估算广东省2009年到医院就诊者中甲型H1N1流感感染数不少于270万例。结论广东省2009年甲型H1N1流感流行高峰出现在11月份,为单月高峰,多数病例临床表现温和,推算在全人群中感染率尚在低水平。     

Challenges of global surveillance during an influenza pandemic

Surveillance is an essential foundation for monitoring and evaluating any disease process, and is especially critical when new disease agents appear. The H1N1 influenza pandemic of 2009 tested the capacities of countries to detect, assess, notify and report events as required by the 2005 International Health Regulations (IHR). As detailed in the IHR, the World Health Organization drew on official reports from Member States as well as unofficial sources (e.g., media alerts) to quickly report and disseminate information about the appearance of the novel influenza virus. The pre-existing Global Influenza Surveillance Network for virological surveillance also provided crucial information for rapid development of a vaccine and for detection of changes in the virus. However, the pandemic also highlighted a number of shortcomings in global epidemiological surveillance for respiratory disease. These included the lack of standards for reporting illness, risk factor and mortality data, and a mechanism for systematic reporting of epidemiological data. Such measures would have facilitated direct comparison of data between countries and improved timely understanding of the characteristics and impact of the pandemic. This paper describes the surveillance strategies in place before the pandemic and the methods that were used at global level to monitor the pandemic. Enhancements of global surveillance are proposed to improve preparedness and response for similar events in the future.     

Estimating and comparing case fatality rates of pandemic influenza A (H1N1) 2009 in its early stage in different countries

Aim

The case fatality rate (CFR) of the novel influenza A (H1N1) 2009 was estimated to gain an understanding of the virulence at the early stage of the pandemic, and it was interpreted and reported primarily as a point estimate without an accompanying measure of precision. To allow proper interpretation of the estimated CFR, the uncertainty inherited from the data sample should be reflected in an inferential conclusion. The aim of this article is to construct confidence limits around the estimates from the sample and then compare the CFR of pandemic influenza A (H1N1) 2009 in its early stage to that in different areas.

Methods

Data were extracted from published papers and WHO pandemic surveillance reports. Statistical method such as the bootstrap approach is used to obtain estimates of confidence intervals.

Results

The estimates of CFR and their confidence intervals in the initial stage of the pandemic are provided for 28 countries (or areas) in this article. The comparison of CFR for 28 countries (or areas) is shown and it is found that the pandemic in South American countries such as Argentina, Uruguay, Costa Rica, Colombia, Paraguay, Dominican Republic, Jamaica, Puerto Rico, were more severe than other countries which had reported cases to corresponding organizations. The analysis shows that the severity of the disease in the USA and Canada has no significant difference.

Conclusion

The CFRs of pandemic influenza A (H1N1) 2009 for 28 countries (or areas) with an accompanying measure of precision are estimated. Therefore, it is possible to compare the severity of pandemic influenza between different countries and to know whether a difference between the severities is significant.     

Influenza surveillance.

The main objectives of influenza surveillance are: to measure the impact of the disease by collection and analysis of epidemiological information on morbidity and mortality, and to anticipate future epidemics and pandemics by the collection and analysis of influenza viruses. The World Health Organization''s influenza programme is based on the collaboration of 98 national influenza centres in 70 countries and the 2 WHO Collaborating Centres in Atlanta and London.     

Does having a seasonal influenza program facilitate pandemic preparedness? An analysis of vaccine deployment during the 2009 pandemic

BackgroundNational seasonal influenza programs have been recommended as a foundation for pandemic preparedness. During the 2009 pandemic, WHO aimed to increase Member States’ equitable access to influenza vaccines through pandemic vaccine donation.MethodsThis analysis explores whether the presence of a seasonal influenza program contributed to more rapid national submission of requirements to receive vaccine during the 2009 influenza pandemic. Data from 2009 influenza vaccine donation, deployment, and surveillance initiatives were collected during May-September 2018 from WHO archival material. Data about the presence of seasonal influenza vaccine programs prior to 2009 were gathered from the WHO-UNICEF Joint Reporting Form. Cox proportional hazards models were used to assess the relationship between presence of a seasonal influenza program and time to submission of a national deployment and vaccination plan and to vaccine delivery.FindingOf 97 countries eligible to receive WHO-donated vaccine, 83 (86%) submitted national deployment and vaccination plans and 77 (79%) received vaccine. Countries with a seasonal influenza vaccine program were more likely to submit a national deployment and vaccination plan (hazards ratio [HR] 2.1; 95% confidence interval [CI]. Countries with regulatory delays were less likely to receive vaccine than those without these delays (HR 0.4, 95% CI: 0.2–0.6).InterpretationDuring the 2009 pandemic, eligible countries with a seasonal influenza vaccine program were more ready to receive and use donated vaccines than those without a program. Our findings suggest that robust seasonal influenza vaccine programs increase national familiarity with the management of influenza vaccines and therefore enhance pandemic preparedness.FundingN/A.     

Comparison of the pandemic H1N1 2009 experience in the Southern Hemisphere with pandemic expectations

Objective: To describe the epidemiological characteristics of the 2009 H1N1 pandemic virus (pH1N1) over the 2009 and 2010 influenza seasons in Australia and New Zealand (NZ) and compare them with expectations based on previous pandemics. Methods: Laboratory‐confirmed influenza and influenza‐like illness (ILI) data were collected from established general practitioner sentinel surveillance schemes in NZ, Victoria and Western Australia (WA) throughout the 2009 and 2010 winter influenza seasons. Respiratory swabs from a sample of ILI patients were tested for influenza type and subtype. ILI rates and laboratory‐confirmed influenza data were analysed by age group and over time. Morbidity, mortality and reproductive number data were collated from the published literature. Results: Peak ILI rates and the percentage of influenza‐positive swabs from ILI patients from all sentinel surveillance schemes were considerably lower in 2010 than 2009. Compared to the population, cases of ILI were over‐represented in the young. While the age distributions in NZ and WA remained consistent, ILI cases were significantly younger in Victoria in 2009 compared to 2010. In Victoria, laboratory‐confirmed pH1N1 comprised up to 97% of influenza‐positive swabs in 2009 but only 56–87% in 2010. Mortality and hospitalisations were lower in 2010. The effective reproduction number (R) for pH1N1 was estimated to be 1.2–1.5 in NZ and WA, similar to estimated R values for seasonal influenza. Data from the surveillance systems indicated differences in the epidemiology of pH1N1 compared to expectations based on previous pandemics. In particular, there was no evidence of a second pandemic wave associated with increased mortality, and complete influenza strain replacement did not occur. Implications: Pandemic planning needs to accommodate the potential for influenza viruses to produce pandemics of various infectiousness and degrees of severity.     

Report of the international forum on pandemic influenza 2010 Qingdao, China, 24-25 July 2010

The 2009 H1N1 influenza pandemic is the first pandemic to hit the world in the 21st century. According to World Health Organization (WHO) reports, as of 18 July 2010, more than 214 countries and overseas territories or communities have reported laboratory confirmed cases of pandemic influenza H1N1 2009, and over 18,336 people have died as a result of the disease [1]. In an effort to facilitate the exchange of strategic and operational experience in the fight against the pandemic, the Chinese Center for Disease Control and Prevention (China CDC), supported by the China Ministry of Health, in collaboration with WHO, the World Bank, the U.S. CDC, and co-organised with the Elsevier Publishing Group, hosted the International Forum on Pandemic Influenza 2010 in July. The two-day meeting, attended by over 600 international delegates, saw human health and animal health professionals discuss the current situation of the pandemic, the global response and vaccination strategies, pandemic surveillance and preparedness, and the animal-human interface in influenza and other emerging infectious diseases. A summary of the discussions is presented here.     

Infection by the pandemic virus (H1N1) 2009 in Andalusia

In April 2009, in response to the WHO's alert due to the existence of human infection cases with a new AH1N1 influenza virus, known as swine flu, Andalusian Health Authorities trigger an specific action plan. The surveillance actions developped provided us with appropriate clinical, epidemiological and virological characteristics of the disease. During the first few days, contingency plans were set up based on epidemiological surveillance and outbreak control measures were adopted through early alert and rapid response systems. After phase 6 was declared, influenza sentinel and severe cases surveillance were used in order to plan healthcare services, to reduce transmission and to identify and protect the most vulnerable population groups. Behaviour of pandemic influenza in Andalusia was similar to that observed in the rest of the world. Atack rate was similar to a seasonal flu and the peak was reached at the 46th/2009 week. Most of them were mild cases and affected particularly to young people. The average age of hospitalised patients was 32. Prior pulmonary disease, smoking and morbid obesity (BMI > 40) were the most common pathologies and risk factors in severe cases. An impact scenario of pandemic wave in Andalusia, with an expected attack rate from 2 to 5%, was prepared considering watt observed in the southern hemisphere. Characteristics of the epidemic concerning its extent, severity and mortality rate were adjusted to this scenario.     

Lessons from pandemic influenza A(H1N1): the research-based vaccine industry's perspective

As A(H1N1) influenza enters the post-pandemic phase, health authorities around the world are reviewing the response to the pandemic. To ensure this process enhances future preparations, it is essential that perspectives are included from all relevant stakeholders, including vaccine manufacturers. This paper outlines the contribution of R&D-based influenza vaccine producers to the pandemic response, and explores lessons that can be learned to improve future preparedness.The emergence of 2009 A(H1N1) influenza led to unprecedented collaboration between global health authorities, scientists and manufacturers, resulting in the most comprehensive pandemic response ever undertaken, with a number of vaccines approved for use three months after the pandemic declaration. This response was only possible because of the extensive preparations undertaken during the last decade.During this period, manufacturers greatly increased influenza vaccine production capacity, and estimates suggest a further doubling of capacity by 2014. Producers also introduced cell-culture technology, while adjuvant and whole virion technologies significantly reduced pandemic vaccine antigen content. This substantially increased pandemic vaccine production capacity, which in July 2009 WHO estimated reached 4.9 billion doses per annum. Manufacturers also worked with health authorities to establish risk management plans for robust vaccine surveillance during the pandemic. Individual producers pledged significant donations of vaccine doses and tiered-pricing approaches for developing country supply.Based on the pandemic experience, a number of improvements would strengthen future preparedness. Technical improvements to rapidly select optimal vaccine viruses, and processes to speed up vaccine standardization, could accelerate and extend vaccine availability. Establishing vaccine supply agreements beforehand would avoid the need for complex discussions during a period of intense time pressure.Enhancing international regulatory co-operation and mutual recognition of approvals could accelerate vaccine supply, while maintaining safety standards. Strengthening communications with the public and healthcare workers using new approaches and new channels could help improve vaccine uptake. Finally, increasing seasonal vaccine coverage will be particularly important to extend and sustain pandemic vaccine production capacity.     

Response to the 2009 pandemic: Effect on influenza control in wealthy and poor countries

The declaration by the World Health Organization (WHO) that appearance of a swine-origin novel influenza virus in 2009 represented a pandemic was based on previously adopted guidelines and the new International Health Regulations. Severity of the pandemic was not part of the definition used, but it was stated to be less than severe at the time of declaration. It was necessary, when there was still uncertainty about the overall impact of the pandemic, for vaccine production to begin to have timely availability. Countries arranged to have vaccine for their populations, and WHO attempted to secure supplies for under-resourced countries.The world had been concerned that the next pandemic might be a severe one, based on the specter of avian influenza with a case fatality of up to 80% in humans. After it was clear that the 2009 pandemic was not severe, there were accusations, especially in Europe, that countries had secured vaccine supplies mainly to benefit the manufacturers. Such charges, even when refuted, may undermine public confidence in the process which assures vaccine supply and availability of vaccine for seasonal use.Production of pandemic vaccine is conditioned on the supply of seasonal influenza vaccine; it is unrealistic to expect vaccine to be available for pandemic use when none is used for seasonal influenza. This particularly applies to poorer counties. They have traditionally not recognized that influenza is a problem, although this attitude is changing. As we go forward, we need to keep in mind the global nature of the threat of influenza. Had the 2009 pandemic been more severe, demand would have been greater and poorer counties would have had little vaccine to meet their needs. Only by taking a broad view of influenza on an annual basis can vaccine supplies be ensured for all countries of the world.     

Protection of trivalent inactivated influenza vaccine against hospitalizations among pandemic influenza A (H1N1) cases in Argentina

The aim of this study was to estimate the effectiveness of 2009 seasonal trivalent inactivated vaccine in reducing hospitalizations due to the novel influenza A H1N1 virus among positive cases. Data collected from Argentina's national epidemiological surveillance system were analyzed. All patients had a clinical diagnosis and underwent positive serological tests for pandemic influenza A H1N1. Logistic regression was used to estimate vaccine effectiveness to prevent severe cases of the disease, measured as hospitalizations. The adjusted effectiveness of the vaccine was 50% (95% CI: 40–59%). Vaccination was significantly associated with hospitalizations in all age groups, and within groups that had and had not received antiviral treatment. These results suggest that seasonal influenza vaccine might have conferred partial protection against severe cases due to the novel pandemic influenza.     

东莞市2009年甲型H1N1流感疫情分析及防制对策探讨

目的对东莞市2009年甲型HIN1流感(简称甲流)疫情及防制措施进行分析,为制定下一步防控策略提供依据。方法疫情资料和监测资料分别来源于东莞市传染病报告系统和流感监测系统,采用描述性流行病学分析方法对其进行分析。结果东莞市首例甲流病例发病时间为6月16日,截至2009年12月31日共发生甲流确诊病例518例,其中重症病例27例、死亡3例;重症病例发生率为5.21%,病死率为0.58%。518例中男性占61.58%,女性占38.42%;学生占75.10%;15岁以下人群占62.74%。3例死亡病例均为学生,均出现神经系统并发症。同期共发生暴发疫情50起(学校47起),罹患率最低为0.87%(32/3 674),最高为17.00%(68/400),暴发疫情中确诊甲流病例260例,占2009年甲流报告总病例数的50.19%。甲流就诊趋势指数及暴发疫情时间分布显示发病高峰为11月份。甲流的流行及防控可分为严防输入、局部暴发及社区扩散、多点暴发和社区流行3个阶段,不同阶段采取了侧重点不同的防控措施。结论东莞市2009年甲流发病的重点人群为15岁以下的学生,暴发疫情主要发生在学校。建议继续加强对流感的监测工作和对监测数据的分析利用,根据疫情进展情况适时调整甲流防控措施。     

A pandemic influenza vaccine in India: from strain to sale within 12 months

In the event of a highly pathogenic influenza pandemic, the Indian subcontinent would need 1.2 billion doses of vaccine to immunize its entire population, double if two doses were required to assure immunity. Serum Institute of India Limited (SII) thus became one of six initial grantees of the World Health Organization (WHO) technology transfer initiative to create capacity in developing countries to manufacture H5N1 pandemic influenza vaccine. At the outbreak of the A(H1N1) 2009 influenza pandemic, experience gained from the H5N1 project was used to develop a live attenuated influenza vaccine (LAIV), since this was the only option for the level of surge capacity required for a large-scale immunization campaign in India. SII took <12 months to develop and market its LAIV intranasal vaccine from receipt of the seed strain from WHO. As of November 2010, over 2.5 million persons have been vaccinated with Nasovac(?) with no serious adverse reactions or vaccine failure after 3 months' post-marketing surveillance. The product has been submitted for prequalification by WHO for purchase by United Nations agencies. In parallel, SII also developed an inactivated influenza vaccine, and is currently looking to ensure the sustainability of its influenza vaccine manufacturing capacity.     

Influenza pandemic (H1N1) 2009 activity during summer 2009. Effectiveness of the 2008-9 trivalent vaccine against pandemic influenza in Spain

Introduction

The Spanish influenza surveillance system (SISS) maintained its activity during the summer of 2009 to monitor the influenza pandemic.

Objectives

To describe pandemic influenza activity from May to September 2009 and to estimate the effectiveness of the 2008-9 seasonal influenza vaccine against laboratory-confirmed pandemic (H1N1) 2009 influenza.

Methods

Data from the SISS were used to identify the trend of pandemic (H1N1) 2009 influenza outside the influenza season. For the effectiveness study, we compared the vaccination status of notified cases [influenza-like illnesses (ILI) laboratory confirmed as pandemic influenza] with that of the test-negative controls.

Results

The first laboratory-confirmed case of the pandemic virus was notified in the system in week 20/2009. The ILI rate increased gradually in the study period, exceeding basic activity in week 38. The proportion of pandemic (H1N1) 2009 influenza viruses detected by the system represented 14% in week 20/2009 and rapidly increased to 90% in week 34. The adjusted vaccine effectiveness of the 2008-9 seasonal vaccine against laboratory-confirmed pandemic influenza was 12% (-30; 41).

Conclusions

The SISS became an essential tool for pandemic monitoring in Spain. The improved SISS will provide more accurate information on influenza activity in future seasonal or pandemic waves. Using surveillance data, we could not demonstrate the effectiveness of the seasonal 2008-9 vaccine against laboratory-confirmed pandemic influenza.     

甲型H1N1流感大流行前后沈阳地区流感病原学流行特征

目的分析甲型H1N1流行性感冒(流感)大流行前后沈阳流感病原学流行特征。方法采集2005年10月—2011年3月连续5.5 a哨点医院的流感样病例咽拭子,进行流感病毒的分离和分型鉴定,并按甲型H1N1流感流行前后划分为3个时期。结果 3个时期共采集流感样病例咽拭子样本6 808份,分离到流感病毒861株,总分离率为12.6%;流行前、流行中和流行后3个时期流感病毒检出率分别为13.8%、18.2%和5.2%。男性和女性流感病毒感染率差异无统计学意义,不同时期流感样病例的年龄构成差异有统计学意义。新的甲型H1N1流感侵袭的人群主要是低年龄组人群,新的甲型H1N1流行期间和流行后,流感季节高峰发生前移。不同年度流感流行毒株型别不同,前1年监测周期的优势株在下1个周期中可被其他型别抑制甚至取代。结论甲型H1N1流感流行后沈阳的流感流行特征已发生了部分改变,这种改变是否持续存在还有待持续监测来得以验证,在2011—2012年监测周期中应密切关注A3(H3N2)亚型和新的甲型H1N1亚型流感毒株的活动情况。