Ravit Bassal

The seroepidemiology of Bordetella pertussis in Israel--Estimate of incidence of infection.

This study was undertaken to estimate the magnitude of Bordetella pertussis infections in a highly vaccinated population in Israel in order to evaluate the relationship between clinical notification data and serology-based evidence of infection. A cross-sectional survey was conducted on a total of 1982 serum samples from the National Serum Bank, collected from January 2000 through December 2001, in order to monitor high levels of pertussis toxin (PT) IgG antibody indicative of recent B. pertussis infection, by standardized methods. The estimation yielded an infection incidence rate of 2448 per 100,000 population (> or =3 years of age) for the year 2000 compared to an annual incidence of reported pertussis of 5.6 per 100,000 for the same period. The peaks of estimated incidence of infection were found in the groups of 15-19-year olds (5245 per 100,000) and older than 60 years (6469 per 100,000), whereas the majority of clinical pertussis cases were reported for the 10-14-year olds (20.5 per 100,000). The findings clearly show that despite a high vaccination coverage rate (>93%), there is still a considerable circulation of B. pertussis, particularly in adolescents and elderly. Population-based serosurveillance for pertussis offers the potential to assist interpretation of trends independent of notification and diagnostic bias.

Helicobacter pylori Infection Is Associated With Low Serum Ferritin Levels in Israeli Arab Children―A Seroepidemiologic Study

We examined the association between Helicobacter pylori seropositivity and low ferritin levels in sera of 509 Israeli Arab children aged 1 to 19 years. Serum ferritin levels were measured using the immunoturbidity assay. ELISA was used to detect serum IgG antibodies to H pylori and IgG antibodies to H pylori CagA+ strains. Low ferritin level was found between 14.5% and 8.6% of the H pylori seropositive and seronegative participants, respectively (P = 0.035). A trend for a higher frequency of low ferritin was detected among H pylori-CagA seropositive children. Multivariate analysis showed an increased frequency of low ferritin only among children younger than or equal to 5 years: adjusted OR 4.62 (95% CI 1.53–13.99) P = 0.007.

The Israeli public health response to wild poliovirus importation

In 2013, a silent wild poliovirus type 1 importation and sustained transmission event occurred in southern Israel. With the aim of preventing clinical poliomyelitis and ensuring virus re-elimination, the public health response to the importation event included intensification of clinical and environmental surveillance activities, enhancement of vaccine coverage, and supplemental immunisation with a bivalent oral polio vaccine against wild poliovirus types 1 and 3. A national campaign launched in August, 2013, resulted in vaccination of 943,587 children younger than 10 years (79% of the eligible target population). Expanded environmental surveillance (roughly 80% population coverage) documented a gradual disappearance of wild poliovirus type 1 in the country from September, 2013, to April, 2014. No paralytic poliomyelitis case was detected. A prompt extensive and coordinated national public health response, implemented on the basis of evidence-based decision making, successfully contained this serious importation and sustained transmission event of wild poliovirus to Israel. On April 28, 2015, WHO officially declared Israel as a polio-free country.

Laboratory Challenges in Response to Silent Introduction and Sustained Transmission of Wild Poliovirus Type 1 in Israel During 2013

Wild poliovirus type 1 (WPV1) introduction into southern Israel in early 2013 was detected by routine environmental surveillance. The virus was identified genetically as related to the South Asian (SOAS) R3A lineage endemic to Pakistan in 2012. Intensified, high-throughput environmental surveillance using advanced molecular methods played a critical role in documenting and locating sustained transmission throughout 2013 and early 2014 in the absence of any acute flaccid paralysis. It guided the public health responses, including stool-based surveillance and serosurveys, to determine the point prevalence in silent excretors and measured the effect of vaccination campaigns with inactivated polio vaccine and bivalent oral polio vaccine on stopping transmission.

Seroepidemiology of Toxoplasma gondii infection in the Israeli population.

Toxoplasmosis seroprevalence varies considerably between countries. We studied the seroprevalence of Toxoplasma gondii IgG antibodies in a national sample of the Israeli population; 2794 sera were tested. The highest age-adjusted seroprevalence rate was in Arabs (non-Bedouins) (60.4%), significantly higher compared to the rate in Jews (19.9%) and Bedouins (27.5%) (P < 0.01). There were no significant gender differences. Seropositivity increased with age in all population groups. For Jews, seropositivity was associated with place of birth and socioeconomic status. A finding of low seroprevalence rate in Bedouins despite their poor living conditions and close contact with livestock is surprising, and might be attributed to the dry and hot climate conditions in their area of residence. In women of reproductive age the seroprevalence was 15.1% in Jews, 25.4% in Bedouins and 72.3% in Arabs (non-Bedouins). Thus, the majority of pregnant women are susceptible to primary infection with T. gondii, and the risk for congenital toxoplasmosis remains high.

Recent trends in the epidemiology of shigellosis in Israel

We provide an update on the epidemiology of shigellosis in Israel using data generated by a sentinel laboratory-based surveillance network for the period 1998-2012. The average annual incidence of culture-proven shigellosis was 97/100 000. We estimated that each case of shigellosis accounted for 25 cases in the community indicating the high burden of disease. Orthodox Jewish communities, living in highly crowded conditions and with a high number of children aged <5 years were the epicentre of country-wide biennial propagated epidemics of S. sonnei shigellosis. S. flexneri was the leading Shigella serogroup in Israeli Arabs. S. flexneri 2a and S. flexneri 6 alternated as the most common serotypes. Both S. sonnei and S. flexneri isolates showed high rates of resistance to ampicillin and trimethoprim/sulfamethoxazole and very low rates of resistance to quinolones and third-generation cephalosporins. Shigellosis due to S. sonnei conferred 81% (95% confidence interval 69-89) protection against the homologous Shigella serotype when epidemic exposure re-occurred 2 years later. These data are of value in the process of Shigella vaccine development.

Interaction Among Ethnicity, Socioeconomic Status, and Helicobacter pylori Seroprevalence in Israeli Children and Adolescents

Objectives: The aim of the study was to examine the prevalence of Helicobacter pylori infection among Israeli children from different backgrounds and to assess potential interactions between ethnicity, socioeconomic status (SES), and H pylori seroprevalence. Patients and Methods: The present sero-epidemiologic study was conducted among 0- to 20-year-old children seeking medical attention, not specifically gastrointestinal symptoms, using sera collected between 2000 and 2001 from 575 Israeli Arab children, 584 Jewish children from the general population, and sera that were obtained between 1997 and 2007 from 464 children of an ultraorthodox Jewish community. An enzyme-linked immunosorbent assay was used to measure H pylori serum immunoglobulin G antibodies and seropositivity to H pylori CagA strains. Results: H pylori seropositivity was 22.9% (95% confidence interval [CI] 19.7–26.5) among Jewish children from the general population, 25.2% (95% CI 21.5–29.4) among ultraorthodox Jewish children, and 45.6% (95% CI 41.5–49.7) among Arab children. H pylori seroprevalence increased significantly with age in the 3 study groups, but it was consistently higher in Arab children. Compared with Jewish participants from high SES and controlling for age and sex, the odds ratio for H pylori seropositivity was 2.03 (95% CI 1.31–3.12) in Jewish children from intermediate SES, 2.42 (95% CI 1.29–4.53) in Arab children from intermediate SES, 2.26 (95% CI 1.52–3.36) in Jewish children from low SES, and 5.72 (95% CI 3.89–8.42) in Arab children from low SES. CagA seropositivity was 40.8% and 45.0% among Jewish and Arab children, respectively (P = 0.59), and it was highest among subjects of lower SES. Conclusions: Socioeconomic factors may not totally explain the ethnic differences in H pylori prevalence.

Significant cross reactive antibodies to influenza virus in adults and children during a period of marked antigenic drift.

BackgroundLittle is known about the development of cross-reactive antibodies following natural exposure to pathogens. Such knowledge is critical in the development of new universal influenza vaccines.MethodsTo study the possibility of the presence of cross-reactive antibodies to influenza viruses which underwent a major antigenic drift between the years 1999 and 2007 sera from samples of 80 children and 400 adults were selected at random from the Israeli national serum bank. The sera was obtained in 2002 and in 2007, two time points that followed a major drift in the infectious H3N2 influenza virus strain (A/Panama/2007/99 to A/Wisconsin/67/2005).ResultsIn the summer of 2002, 13% of the children had Hemagglutination Inhibition (HI) antibody titers of at least 40 and these antibodies recognized both A/Panama/2007/99 and A/Wisconsin/67/2005, where the latter strain only began to circulate in Israel in 2006. In 2007, 29% of the children had HI antibody titers of at least 40 directed against both A/Wisconsin/67/2005 and A/Panama/2007/99, even though they had never been exposed to the latter virus. Anti-A/Panama/2007/99 antibodies were detected in 58% and 68% of the 2002 and 2007 adult samples, respectively, while 8% and 39% had antibodies against A/Wisconsin/67/2005, respectively.ConclusionsThe presence of naturally occurring cross-reactive influenza virus antibodies in a significant percentage of children has important implications for the development of a universal influenza vaccine.

Comparing three basic models for seasonal influenza

In this paper we report the use of the open source Spatiotemporal Epidemiological Modeler (STEM, www.eclipse.org/stem) to compare three basic models for seasonal influenza transmission. The models are designed to test for possible differences between the seasonal transmission of influenza A and B. Model 1 assumes that the seasonality and magnitude of transmission do not vary between influenza A and B. Model 2 assumes that the magnitude of seasonal forcing (i.e., the maximum transmissibility), but not the background transmission or flu season length, differs between influenza A and B. Model 3 assumes that the magnitude of seasonal forcing, the background transmission, and flu season length all differ between strains. The models are all optimized using 10 years of surveillance data from 49 of 50 administrative divisions in Israel. Using a cross-validation technique, we compare the relative accuracy of the models and discuss the potential for prediction. We find that accounting for variation in transmission amplitude increases the predictive ability compared to the base. However, little improvement is obtained by allowing for further variation in the shape of the seasonal forcing function.

Epidemiological and Virological Characterization of Influenza B Virus Infections.

While influenza A viruses comprise a heterogeneous group of clinically relevant influenza viruses, influenza B viruses form a more homogeneous cluster, divided mainly into two lineages: Victoria and Yamagata. This divergence has complicated seasonal influenza vaccine design, which traditionally contained two seasonal influenza A virus strains and one influenza B virus strain. We examined the distribution of the two influenza B virus lineages in Israel, between 2011–2014, in hospitalized and in non-hospitalized (community) influenza B virus-infected patients. We showed that influenza B virus infections can lead to hospitalization and demonstrated that during some winter seasons, both influenza B virus lineages circulated simultaneously in Israel. We further show that the influenza B virus Yamagata lineage was dominant, circulating in the county in the last few years of the study period, consistent with the anti-Yamagata influenza B virus antibodies detected in the serum samples of affected individuals residing in Israel in the year 2014. Interestingly, we found that elderly people were particularly vulnerable to Yamagata lineage influenza B virus infections.