Theodore F. Tsai

OBJECTIVE: To update the estimated global incidence of Japanese encephalitis (JE) using recent data for the purpose of guiding prevention and control efforts. METHODS: Thirty-two areas endemic for JE in 24 Asian and Western Pacific countries were sorted into 10 incidence groups on the basis of published data and expert opinion. Population-based surveillance studies using laboratory-confirmed cases were sought for each incidence group by a computerized search of the scientific literature. When no eligible studies existed for a particular incidence group, incidence data were extrapolated from related groups. FINDINGS: A total of 12 eligible studies representing 7 of 10 incidence groups in 24 JE-endemic countries were identified. Approximately 67,900 JE cases typically occur annually (overall incidence: 1.8 per 100,000), of which only about 10% are reported to the World Health Organization. Approximately 33,900 (50%) of these cases occur in China (excluding Taiwan) and approximately 51,000 (75%) occur in children aged 0-14 years (incidence: 5.4 per 100,000). Approximately 55,000 (81%) cases occur in areas with well established or developing JE vaccination programmes, while approximately 12,900 (19%) occur in areas with minimal or no JE vaccination programmes. CONCLUSION: Recent data allowed us to refine the estimate of the global incidence of JE, which remains substantial despite improvements in vaccination coverage. More and better incidence studies in selected countries, particularly China and India, are needed to further refine these estimates.

Hemorrhagic fever with renal syndrome (HFRS) comprises a variety of clinically similar diseases of viral etiology that are endemic to and sporadically epidemic throughout the Eurasian continent and Japan. Although HFRS has not been reported in North America, viruses that are antigenically similar to HFRS agents were recently isolated from rodents in the United States. Examination and comparison of eight representative isolates from endemic disease areas and from regions with no known associated HFRS indicate that these viruses represent a new and unique group that constitutes a separate genus in the Bunyaviridae family of animal viruses.

In September and October, 1976, an outbreak of illness due to chocolate milk contaminated with Yersinia enterocolitica resulted in hospitalization of 36 children, 16 of whom had appendectomies. Infection with Y. enterocolitica serotype 0:8 was demonstrated in 38 ill persons. Sixty-one per cent of the persons who were infected had a titer greater than 1:160 OH agglutinins to serotype 8 yersinia, whereas 48 per cent of the hospitalized children had a fourfold change in agglutinin titer. An epidemiologic investigation demonstrated that illness was associated with drinking of chocolate milk purchased in school cafeterias, and Y. enterocolitica 0:8 was subsequently isolated from the milk. The investigation suggested that the bacterium was introduced at the dairy during the mixing by hand of chocolate syrup with previously pasteurized milk.

INTRODUCTION: The hemagglutination inhibition (HI) titer of 1:40, which has been recognized as an immunologic correlate corresponding to a 50% reduction in the risk of contracting influenza, is based on studies in adults. Neither seasonal nor challenge-based correlates have been evaluated in children. METHODS: A total of 4707 influenza vaccine-naive healthy children 6 to 72 months old were randomized in a ratio of 2:2:1 to receive 2 doses of MF-59-adjuvanted influenza vaccine (Novartis Vaccines), trivalent inactivated influenza vaccine subunit (trivalent inactivated influenza vaccine control, GSK), or a saline placebo during the 2007 to 2008 and 2008 to 2009 influenza seasons. The second dose was given 30 days after dose 1. Clinical influenza-like illnesses cases identified by active surveillance were confirmed by reverse transcription polymerase chain reaction testing for influenza. Vaccine immunogenicity 50 days after dose 1 was evaluated in a subset of 777 children. RESULTS: Immunogenicity and efficacy results for H3N2 were evaluated against the Prentice criteria, which confirmed that the immunogenicity results warranted estimation of an immunologic correlate. We then used the Dunning model fitting the H3N2 antibody titers at day 50 and the influenza cases observed in the immunogenicity subset to estimate a correlate of protection. This analysis revealed that a cutoff HI titer of 1:110 was associated with the conventional 50% clinical protection rate against infection during the entire season, and titers of 1:215, 1:330, and 1:629 predicated protection rates of 70%, 80%, and 90%, respectively. The conventional adult HI titer of 1:40 was only associated with 22% protection. CONCLUSIONS: The use of the 1:40 HI adult correlate of protection is not appropriate when evaluating influenza vaccines in children. Although a cutoff of 1:110 may be used to predict the conventional 50% clinical protection rate, a titer of 1:330 would predict an 80% protective level, which would seem to be more desirable from a public health perspective.