Vaccine Coverage Associated With Ending a Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Wave: A Retrospective Longitudinal Analysis.

BACKGROUND: Two SARS-CoV-2 waves in Israel ended while a substantial number of individuals remained unvaccinated or partially vaccinated. The indirect protective effect of the first BNT162b2 vaccination campaign in Israel was evaluated between 22 December 2020 and 18 May 2021. METHODS: The daily percentage of new polymerase chain reaction (PCR)-confirmed SARS-CoV-2 cases among unvaccinated individuals was analyzed for trends. Major shifts were identified using piecewise linear regression analysis. At these shifts, the percentage of naturally vaccinated (past SARS-CoV-2 cases) and the percentage of actively vaccinated (by inoculation) individuals were weighted and summed to determine the percentage of natural and active vaccination (NAV). RESULTS: A first decline among unvaccinated individuals occurred during a lockdown period, when the percentage of NAV was 8.16%. The major decline occurred after the end of the lockdown when the percentage of NAV reached 52.05%. SARS-CoV-2 cases ultimately declined among unvaccinated individuals when the percentage of NAV reached 63.55%. During the study period, the Alpha variant was prevalent and the use of nonpharmaceutical interventions, including social distancing, existed to varying degrees. CONCLUSIONS: The vaccination campaign played a major role in the decline of SARS-CoV-2 infection among unvaccinated individuals, leading to the end of the first 2021 SARS-CoV-2 wave (Alpha variant) in Israel. Infection in unvaccinated individuals stopped when two-thirds of the population were naturally or actively vaccinated. Any change in characteristics of the virus or the population can lead to a new outbreak.

Effectiveness of BNT162b2 Vaccine Booster against SARS-CoV-2 Infection and Breakthrough Complications, Israel.

We estimated vaccine effectiveness (VE) of the BNT162b2 (Pfizer-BioNTech, https://www.pfizer.com) booster dose against SARS-CoV-2 infection and reduction of complications (hospitalization, severe disease, and death) among breakthrough cases in persons in Israel >16 years of age for <20 weeks. VE estimates reached 96.8% (95% CI 96.0%-97.5%) for persons 16-59 years of age and 93.1% (95% CI 91.8%-94.2%) for persons >60 years of age on week 3. VE estimates remained at these levels for 8 weeks in the 16-59 age group and 11 weeks in those >60. A slow decline followed, becoming more pronounced in the last 2-3 weeks of evaluation. Estimates in the last week of evaluation were 77.6% (95% CI 68.4%-84.2%) and 61.3% (52.5%-68.4%) for persons 16-59 years and >60 years, respectively. The more pronounced VE decline coincided with rapid increase in Omicron variant activity. Rate reduction of breakthrough complications remained moderate to high throughout the evaluation.

Premature mortality attributable to COVID-19: potential years of life lost in 17 countries around the world, January-August 2020.

BACKGROUND: Understanding the impact of the burden of COVID-19 is key to successfully navigating the COVID-19 pandemic. As part of a larger investigation on COVID-19 mortality impact, this study aims to estimate the Potential Years of Life Lost (PYLL) in 17 countries and territories across the world (Australia, Brazil, Cape Verde, Colombia, Cyprus, France, Georgia, Israel, Kazakhstan, Peru, Norway, England & Wales, Scotland, Slovenia, Sweden, Ukraine, and the United States [USA]). METHODS: Age- and sex-specific COVID-19 death numbers from primary national sources were collected by an international research consortium. The study period was established based on the availability of data from the inception of the pandemic to the end of August 2020. The PYLL for each country were computed using 80 years as the maximum life expectancy. RESULTS: As of August 2020, 442,677 (range: 18-185,083) deaths attributed to COVID-19 were recorded in 17 countries which translated to 4,210,654 (range: 112-1,554,225) PYLL. The average PYLL per death was 8.7 years, with substantial variation ranging from 2.7 years in Australia to 19.3 PYLL in Ukraine. North and South American countries as well as England & Wales, Scotland and Sweden experienced the highest PYLL per 100,000 population; whereas Australia, Slovenia and Georgia experienced the lowest. Overall, males experienced higher PYLL rate and higher PYLL per death than females. In most countries, most of the PYLL were observed for people aged over 60 or 65 years, irrespective of sex. Yet, Brazil, Cape Verde, Colombia, Israel, Peru, Scotland, Ukraine, and the USA concentrated most PYLL in younger age groups. CONCLUSIONS: Our results highlight the role of PYLL as a tool to understand the impact of COVID-19 on demographic groups within and across countries, guiding preventive measures to protect these groups under the ongoing pandemic. Continuous monitoring of PYLL is therefore needed to better understand the burden of COVID-19 in terms of premature mortality.

The impact of SARS-CoV-2 on respiratory syndromic and sentinel surveillance in Israel, 2020: a new perspective on established systems.

BackgroundThe COVID-19 pandemic presented new challenges for the existing respiratory surveillance systems, and adaptations were implemented. Systematic assessment of the syndromic and sentinel surveillance platforms during the pandemic is essential for understanding the value of each platform in the context of an emerging pathogen with rapid global spread.AimWe aimed to evaluate systematically the performance of various respiratory syndromic surveillance platforms and the sentinel surveillance system in Israel from 1 January to 31 December 2020.MethodsWe compared the 2020 syndromic surveillance trends to those of the previous 3 years, using Poisson regression adjusted for overdispersion. To assess the performance of the sentinel clinic system as compared with the national SARS-CoV-2 repository, a cubic spline with 7 knots and 95% confidence intervals were applied to the sentinel network's weekly percentage of positive SARS-CoV-2 cases.ResultsSyndromic surveillance trends changed substantially during 2020, with a statistically significant reduction in the rates of visits to physicians and emergency departments to below previous years' levels. Morbidity patterns of the syndromic surveillance platforms were inconsistent with the progress of the pandemic, while the sentinel surveillance platform was found to reflect the national circulation of SARS-CoV-2 in the population.ConclusionOur findings reveal the robustness of the sentinel clinics platform for the surveillance of the main respiratory viruses during the pandemic and possibly beyond. The robustness of the sentinel clinics platform during 2020 supports its use in locations with insufficient resources for widespread testing of respiratory viruses.

Monitoring SARS-CoV-2 Activity with Sentinel Surveillance: Lessons Learned from the First Wave in Israel.

BACKGROUND: Guidelines for pandemic preparedness emphasize the role of sentinel and syndromic surveillance in monitoring pandemic spread. OBJECTIVES: To examine advantages and obstacles of utilizing a sentinel influenza surveillance system to monitor community severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) activity based on Israel's experience from mid-March to mid-May 2020. METHODS: Several modifications were applied to the influenza surveillance system. The clinical component relied mainly on pneumonia and upper respiratory infection (URI) consultations with primary care physicians as well as visits to emergency departments (ED) due to pneumonia. The virological data were based on nasopharyngeal swabs obtained from symptomatic patients who visited outpatient clinics. RESULTS: By week 12 of the pandemic, the crude and age-specific primary physician consultation rates due to URI and pneumonia declined below the expected level, reaching nadir that lasted from week 15 until week 20. Similarly, ED visits due to pneumonia were significantly lower than expected from weeks 14 and 15 to week 20. The virological surveillance started on week 13 with 6/253 of the swabs (2.3%) positive for SARS-CoV-2. There was a peak of 13/225 positive swabs on week 145.8%. During weeks 17-20, none of the swabs (47-97 per week) were positive for SARS-CoV-2. This trend was similar to national data. CONCLUSIONS: The virological component of the surveillance system showed the SARS-CoV-2 community spread, but had low sensitivity when virus activity was low. The clinical component, however, had no yield. Sentinel surveillance can assist in monitoring future novel pandemics and should be augmented in revised preparedness plans.

Effectiveness of BNT162b2 Vaccine in Adolescents during Outbreak of SARS-CoV-2 Delta Variant Infection, Israel, 2021.

In Israel, the BNT162b2 vaccine against severe acute respiratory syndrome coronavirus 2 was approved for use in adolescents in June 2021, shortly before an outbreak of B.1.617.2 (Delta) variant-dominant infection. We evaluated short-term vaccine effectiveness and found the vaccine to be highly effective among this population in this setting.

Delayed respiratory syncytial virus epidemic in children after relaxation of COVID-19 physical distancing measures, Ashdod, Israel, 2021.

Following low incidence of respiratory syncytial virus (RSV) infections in 2020 during the COVID-19 pandemic, we noted a resurgence in hospitalised children in spring/summer 2021 following relaxation of public health measures. We compared this outbreak to previous autumn/winter seasons. We found higher weekly case numbers and incidence rates, more cases from urban neighbourhoods with lower socioeconomic status, and similar clinical presentation and severity. Public health implications include the re-evaluation of palivizumab administration and the need for surge capacity planning.

Application of the double kernel density approach to the analysis of cancer incidence in a major metropolitan area.

RATIONALE: Although cancer is a main cause of human morbidity worldwide, relatively small numbers of new cancer cases are recorded annually in single urban areas. This makes the association between cancer morbidity and environmental risk factors, such as ambient air pollution, difficult to detect using traditional methods of analysis based on age standardized rates and zonal estimates. STUDY GOAL: The present study investigates the association between air pollution and cancer morbidity in the Greater Haifa Metropolitan Area in Israel by comparing two analytical techniques: the traditional zonal approach and more recently developed Double Kernel Density (DKD) tools. While the first approach uses age adjusted Standardized Incidence Ratios (SIRs) for small census areas, the second approach estimates the areal density of cancer cases, normalized by the areal density of background population in which cancer events occurred. Both analyses control for several potential confounders, including air pollution, proximities to main industrial facilities and socio-demographic attributes. RESULTS: Air pollution variables and distances to industrial facilities emerged as statistically significant predictors of lung and NHL cancer morbidity in the DKD-based models (p<0.05) but not in the models based on SIRs estimates (p>0.2). CONCLUSION: DKD models appear to be a more sensitive tool for assessing potential environmental risks than traditional SIR-based models, because DKD estimates do not depend on a priory geographic delineations of statistical zones and produce a smooth and continuous disease 'risk surface' covering the entire study area. We suggest using the DKD method in similar studies of the effect of ambient air pollution on chronic morbidity, especially in cases in which the number of statistical areas available for aggregation and comparison is small and recorded morbidity events are relatively rare.

Recent trends of cervical cancer and Cervical Intraepithelial Neoplasia 3 (CIN3) in Israel.

PURPOSE: This study describes time trends of cervical cancer and Cervical Intraepithelial Neoplasia 3 (CIN3) in Israel in the years 1986-2010 and characterizes these patients by demographics. METHODS: A retrospective survey based on cervical cancer and CIN3 data documented in the computerized system of the second largest Health Maintenance Organizations (HMO) in Israel, "Maccabi Healthcare Services" (MHS) between 1986 and 2010. RESULTS: 737 cervical cancer patients and 3,459 patients of CIN3 were reported between 1986 and 2010. The mean age of women with cervical cancer was significantly higher (mean 49.1 years) than that of CIN3 patients (mean 36.3 years) (p-value < 0.0001). The annual age-adjusted incidence rate of cervical cancer increased significantly from 1.6 per 100,000 in 1986 to 3.7 per 100,000 in 2010 (p for trend = 0.0001) and for CIN3, from 3.9 per 100,000 in 1986 to 40.4 per 100,000 in 2010 (p for trend = 0.0001). For cervical cancer, using the Joinpoint software we demonstrated an increase in the age-adjusted incidence rate between 1986 and 2003 and since then, a decrease was observed. Cervical cancer and CIN3 were mostly common in the Tel Aviv District. CONCLUSIONS: Although quite low to begin with, the incidence rates of cervical cancer and CIN3 in Israel may be further lowered by implementing an organized screening program and introduction of the HPV vaccine into the national immunization program.

[Syndromic surveillance in public health practice--an updated view].

Syndromic surveillance systems which were developed as part of bioterrorism preparedness initiatives originally focused on early detection. However, the early detection capabilities of such systems proved to be limited, particularly for small-scale outbreaks. On the other hand, syndromic surveillance systems proved to be very effective in situational awareness and in supporting decision making. Today, syndromic surveillance is being implemented in public health practice as a routine tool, working in concert with the traditional surveillance systems.

Impact of the COVID-19 pandemic on total, sex- and age-specific all-cause mortality in 20 countries worldwide during 2020: results from the C-MOR project.

BACKGROUND: To understand the impact of the COVID-19 pandemic on mortality, this study investigates overall, sex- and age-specific excess all-cause mortality in 20 countries, during 2020. METHODS: Total, sex- and age-specific weekly all-cause mortality for 2015-2020 was collected from national vital statistics databases. Excess mortality for 2020 was calculated by comparing weekly 2020 observed mortality against expected mortality, estimated from historical data (2015-2019) accounting for seasonality, long- and short-term trends. Crude and age-standardized rates were analysed for total and sex-specific mortality. RESULTS: Austria, Brazil, Cyprus, England and Wales, France, Georgia, Israel, Italy, Northern Ireland, Peru, Scotland, Slovenia, Sweden, and the USA displayed substantial excess age-standardized mortality of varying duration during 2020, while Australia, Denmark, Estonia, Mauritius, Norway, and Ukraine did not. In sex-specific analyses, excess mortality was higher in males than females, except for Slovenia (higher in females) and Cyprus (similar in both sexes). Lastly, for most countries substantial excess mortality was only detectable (Austria, Cyprus, Israel, and Slovenia) or was higher (Brazil, England and Wales, France, Georgia, Italy, Northern Ireland, Sweden, Peru and the USA) in the oldest age group investigated. Peru demonstrated substantial excess mortality even in the <45 age group. CONCLUSIONS: This study highlights that excess all-cause mortality during 2020 is context dependent, with specific countries, sex- and age-groups being most affected. As the pandemic continues, tracking excess mortality is important to accurately estimate the true toll of COVID-19, while at the same time investigating the effects of changing contexts, different variants, testing, quarantine, and vaccination strategies.

Excess all-cause mortality and COVID-19-related mortality: a temporal analysis in 22 countries, from January until August 2020.

BACKGROUND: This study aimed to investigate overall and sex-specific excess all-cause mortality since the inception of the COVID-19 pandemic until August 2020 among 22 countries. METHODS: Countries reported weekly or monthly all-cause mortality from January 2015 until the end of June or August 2020. Weekly or monthly COVID-19 deaths were reported for 2020. Excess mortality for 2020 was calculated by comparing weekly or monthly 2020 mortality (observed deaths) against a baseline mortality obtained from 2015-2019 data for the same week or month using two methods: (i) difference in observed mortality rates between 2020 and the 2015-2019 average and (ii) difference between observed and expected 2020 deaths. RESULTS: Brazil, France, Italy, Spain, Sweden, the UK (England, Wales, Northern Ireland and Scotland) and the USA demonstrated excess all-cause mortality, whereas Australia, Denmark and Georgia experienced a decrease in all-cause mortality. Israel, Ukraine and Ireland demonstrated sex-specific changes in all-cause mortality. CONCLUSIONS: All-cause mortality up to August 2020 was higher than in previous years in some, but not all, participating countries. Geographical location and seasonality of each country, as well as the prompt application of high-stringency control measures, may explain the observed variability in mortality changes.

Respiratory Syncytial Virus hospitalization burden: a nation-wide population-based analysis, 2000-2017.

OBJECTIVES: Respiratory Syncytial Virus (RSV) is a known cause of morbidity among young children, while RSV-related disease in the elderly is not fully recognized. Several RSV candidate vaccines for infants, pregnant women and adults are under development. We aimed to estimate nationwide age-specific hospitalizations and seasonal trends, to help determine the optimal age for vaccination. METHODS: Hospitalizations with a primary RSV-related diagnoses were retrieved from the National Hospital Database for the years 2000-2017. Data were analyzed by year, month and age group to determine hospitalization rates and seasonal trends. RESULTS: During the analysis period, 39,156 hospitalizations received primary RSV-related ICD-9 diagnostic codes. The highest mean yearly hospitalization rate occurred among infants <1 year of life (1,218.4 per 100,000). Within the first year of life, the highest mean yearly hospitalization rate was observed in the second month of life (3,541.5 hospitalizations per 100,000). Hospitalization rates for individuals ≥5 years old increased during the study period, primarily among patients ≥65 years of age, reaching hospitalization rate of 9 per 100,000 in 2017. A clear seasonal pattern was observed. CONCLUSIONS: An effective vaccine for infants and pregnant women has the potential to reduce hospitalizations burden. RSV-related hospitalizations burden among adults requires additional research.

[Clinical and virological surveillance of influenza in Israel--implementation during pandemic influenza].

BACKGROUND: Pandemic influenza surveillance has a central role in providing an updated situation for the health care system. AIM: To describe the Israel Center for Disease Control (ICDC) pandemic influenza surveillance system. METHODS: The ICDC conducts a seasonal influenza surveillance system based on patients' visits to community clinics (mainly Maccabi Healthcare Services) and emergency rooms for influenza-like illness (ILI) or pneumonia, and on laboratory confirmed nasopharyngeal swabs from ILI patients at designated sentinel clinics (tested at the Central Virology Laboratory). The laboratory based surveillance provides data on the active influenza strains, resistance to anti-viral drugs and match with the seasonal vaccine. The influenza surveillance network was strengthened since the level of the influenza pandemic alert was raised to phase 4 at the end of April 2009. RESULTS: The first A/H1N1 2009 cases were identified by the surveillance system in the last week of May 2009. Local transmission was recorded in the second half of June 2009. At this time there was an increase in the rates of patient visits to outpatient clinics for ILI, especially in the age group 0-18 years old and in residents of Tel Aviv, Central and Jerusalem districts. By the end of July 2009 there was an increase in pneumonia cases (mainly 2-18 years old) in community clinics. CONCLUSIONS: Once the pandemic influenza began spreading, the ICDC surveillance system provided a valid picture which facilitated the decision to stop laboratory confirmation of each community case and rely on the ICDC surveillance system as the main source for information.

Evaluation of a syndromic surveillance system using the WSARE algorithm for early detection of an unusual, localized summer outbreak of influenza B: implications for bioterrorism surveillance.

BACKGROUND: Syndromic surveillance systems have been developed for early detection of bioterrorist attacks, but few validation studies exist for these systems and their efficacy has been questioned. OBJECTIVES: To assess the capabilities of a syndromic surveillance system based on community clinics in conjunction with the WSARE algorithm in identifying early signals of a localized unusual influenza outbreak. METHODS: This retrospective study used data on a documented influenza B outbreak in an elementary school in central Israel. The WSARE algorithm for anomalous pattern detection was applied to individual records of daily patient visits to clinics of one of the four health management organizations in the country. RESULTS: Two successive significant anomalies were detected in the HMO's data set that could signal the influenza outbreak. If data were available for analysis in real time, the first anomaly could be detected on day 3 of the outbreak, 1 day after the school principal reported the outbreak to the public health authorities. CONCLUSIONS: Early detection is difficult in this type of fast-developing institutionalized outbreak. However, the information derived from WSARE could help define the outbreak in terms of time, place and the population at risk.

Spatial distribution of West Nile virus in humans and mosquitoes in Israel, 2000-2014.

OBJECTIVES: Israel has a long history of West Nile virus (WNV) morbidity, and the rate of detection of WNV in mosquitoes has been high since 2000. The aim of this study was to integrate several WNV datasets in order to gain an insight into the geographical distribution of WNV in Israel. METHODS: Three choropleth maps were generated showing WNV human morbidity, WNV prevalence in mosquitoes, and the results of a nationwide serological survey, based on the division of Israel into 15 sub-districts. RESULTS: The maps show a high endemicity of WNV in Israel. In respect to the morbidity map, the population residing in the central part of the country and in Arava Region is at higher risk of developing the disease than the population of the rest of Israel. Interestingly, high prevalence rates of both WNV serology and WNV-infected mosquitoes were detected in Arava Region, but lower prevalence rates were detected in most areas of the coastal region, suggesting that other factors might also be important in the development of symptomatic WNV infections. CONCLUSIONS: These results underline the high prevalence of WNV in Israel and point to specific risk areas for WNV infections across the country.

The seroprevalence of West Nile Virus in Israel: A nationwide cross sectional study.

West Nile Virus (WNV) is endemic in Israel, affecting yearly 40-160 individuals. Israel is located on a central migratory path between Africa and Eurasia and most West Nile Fever (WNF) cases reported in recent years were among residents of the coastal plain. The aim of the study was to evaluate the seroprevalence of WNV among the Israeli population and to assess correlates for WNV infection. A cross-sectional nationwide serologic survey was conducted using 3,145 serum samples collected by the national Israeli serum bank during 2011-2014, representing all age and population groups in Israel. Prevalence rates of WNV IgG antibodies were determined. Logistic regressions models were applied to assess the associations between demographic characteristics and WNV seropositivity. 350 samples were positive to WNV (11.1%; 95%CI: 10.0-12.3%). In the multivariable analysis, there was a significant association between seropositivity and the Arab population group vs. Jews and others (OR = 1.86, 95%CI: 1.37-2.52), the time lived in Israel [50-59 years vs. 0-9 years; OR = 10.80 (95%CI: 1.03-113.46) and ≥60 years vs. 0-9 years; OR = 14.00 (1.32-148.31)] residence area] Coastal Plain, Inland Plain (Shfela) and Great Rift Valley vs. Upper Galilee; OR = 2.24 (95%CI: 1.37-3.65), OR = 2.18 (95%CI: 1.18-4.03), OR = 1.90 (95%CI: 1.10-3.30), respectively [and rural vs. urban settlement (OR = 1.65, 95%CI: 1.26-2.16). People, who reside in the Coastal Plain, Inland Plain and Great Rift Valley, should be aware of the risk of contracting WNV and reduce exposure to mosquito bites, using insect repellents, and wearing protective clothing. The Ministry of Environmental Protection should be active in reducing the mosquito population by eliminating sources of standing water, a breeding ground for mosquitoes.

Influenza Season Hospitalization Trends in Israel: A Multi-Year Comparative Analysis 2005/2006 Through 2012/2013.

BACKGROUND: Influenza-related morbidity impacts healthcare systems, including hospitals. OBJECTIVE: To obtain a quantitative assessment of hospitalization burden in pediatric and internal medicine departments during influenza seasons compared with the summer months in Israel. METHODS: Data on pediatric and internal medicine hospitalized patients in general hospitals in Israel during the influenza seasons between 2005 and 2013 were analyzed for rate of hospitalizations, rate of hospitalization days, hospital length of stay (LOS), and bed occupancy and compared with the summer months. Data were analyzed for hospitalizations for all diagnoses, diagnoses of respiratory or cardiovascular disease (ICD9 390-519), and influenza or pneumonia (ICD9480-487), with data stratified by age. The 2009-2010 pandemic influenza season was excluded. RESULTS: Rates of monthly hospitalizations and hospitalization days for all diagnoses were 4.8% and 8% higher, respectively, during influenza seasons as compared with the summers. The mean LOS per hospitalization for all diagnoses demonstrated a small increase during influenza seasons as compared with summer seasons. The excess hospitalizations and hospitalization days were especially noticed for the age groups under 1 year, 1-4 years, and 85 years and older. The differences were severalfold higher for patients with a diagnosis of respiratory or cardiovascular disease and influenza or pneumonia. Bed occupancy was higher during influenza seasons compared with the summer, particularly in pediatric departments. CONCLUSIONS: Hospital burden in pediatric and internal medicine departments during influenza seasons in Israel was associated with age and diagnosis. These results are important for optimal preparedness for influenza seasons.

Estimating the usual prevalence and incidence of acute illness in the community: implications for pandemic influenza and bioterrorism preparedness.

BACKGROUND: Early clinical signs of influenza caused by a pandemic strain will presumably not differ significantly from those caused by other respiratory viruses. Similarly, early signs of diseases that may result from bioterrorism are frequently non-specific and resemble those of influenza-like illness. Since the time window for effective intervention is narrow, treatment may need to be initiated prior to a definitive diagnosis. Consequently, planning of medications, manpower and facilities should also account for those who would be treated for an unrelated acute illness. OBJECTIVES: To estimate usual patterns of acute illness in the community as a baseline for integration into pandemic influenza and bioterrorism preparedness plans. METHODS: Between 2000 and 2003 we conducted 13 telephone surveys to estimate the usual incidence and prevalence of symptoms of acute illness in the community. RESULTS: On average, 910 households were included in each of the surveys, representing about 3000 people. The compliance rates for full interviews ranged from 72.3% to 86.0%. In winter, on average, about 2% of the Israeli population (individuals) suffered each day from fever of > or = 38 degrees C, and about 0.8% during the other months. The prevalence of cough was higher, 9.2% in winter and 3% during summer. Daily incidence of fever ranged from about 0.4% per day in winter to about 0.2% in the fall. The prevalence and incidence of both fever and cough were highest for infants followed by children aged 1-5 years. CONCLUSIONS: These background morbidity estimates can be used for planning the overall treatment requirements, in addition to actual cases resulting from pandemic influenza or a bioterrorist incident.

A large food-borne outbreak of group A streptococcal pharyngitis in an industrial plant: potential for deliberate contamination.

Contamination of food with streptococci could present with unusual outbreaks that may be difficult to recognize in the early stages. This is demonstrated in a large food-borne outbreak of streptococcal pharyngitis that occurred in 2003 in a factory in Israel. The outbreak was reported to the public health services on July 2 and an epidemiologic investigation was initiated. Cases and controls were interviewed and throat swabs were taken. An estimated 212 cases occurred within the first 4 days, the peak occurring on the second day. There was a wave of secondary cases during an additional 11 days. The early signs were of a respiratory illness including sore throat, weakness and fever, with high absenteeism rates suggesting a respiratory illness. As part of a case-control study, cases and controls were interviewed and throat swabs taken. Illness was significantly associated with consumption of egg-mayonnaise salad (odds ratio 4.2, 95% confidence interval 1.4-12.6), suggesting an incubation period of 12-96 hours. The initial respiratory signs of food-borne streptococcal pharyngitis outbreaks could delay the identification of the vehicle of transmission. This could be particularly problematic in the event of deliberate contamination.