Robust reconstruction and analysis of outbreak data: influenza A(H1N1)v transmission in a school-based population.

The rapid spread of the new influenza virus A(H1N1)v in young age groups in 2009 has been partly attributed to a high transmission intensity in schools. However, detailed characterization of the spread of influenza in school populations has been difficult to obtain, simply because it is very hard to identify who infected whom in a large outbreak. Data collected in large outbreak investigations typically miss many transmission events, and some reported transmission events will be incorrect. Here the authors present robust likelihood-based methods that can be used to analyze outbreak data while explicitly accounting for both missing data and erroneous data. They apply this method to a school-based outbreak of pandemic influenza A(H1N1)v that occurred in London, United Kingdom, in April 2009. The authors show that the generation interval in this school-based population was 2.20 days and that the reproduction number declined coincident with school closure, from 1.33 secondary cases per primary case to 0.43 secondary cases per primary case. These results provide quantitative evidence for the change in influenza transmission that is to be expected from school closure.

Oseltamivir-resistant pandemic (H1N1) 2009 virus infection in England and Scotland, 2009-2010.

Oseltamivir has been widely used for pandemic (H1N1) 2009 virus infection, and by April 30, 2010, a total of 285 resistant cases were reported worldwide, including 45 in the United Kingdom. To determine risk factors for emergence of oseltamivir resistance and severe infection, a case-control study was conducted in the United Kingdom. Study participants were hospitalized in England or Scotland during January 4, 2009-April 30, 2010. Controls had confirmed oseltamivir-sensitive pandemic (H1N1) 2009 virus infections, and case-patients had confirmed oseltamivir-resistant infections. Of 28 case-patients with available information, 21 (75%) were immunocompromised; 31 of 33 case-patients (94%) received antiviral drugs before a sample was obtained. After adjusting for confounders, case-patients remained significantly more likely than controls to be immunocompromised and at higher risk for showing development of respiratory complications. Selective drug pressure likely explains the development of oseltamivir resistance, especially among immunocompromised patients. Monitoring of antiviral resistance is strongly recommended in this group.

Outbreak of Q fever, Florac, Southern France, Spring 2007.

INTRODUCTION: In May 2007, five patients with Q fever-like symptoms were reported in an agricultural educational center in the rural southern French town of Florac. An investigation was undertaken to identify the outbreak source and risk factors for infection, and to implement control measures. MATERIALS AND METHODS: We undertook active case finding. Patients were defined as individuals with an unexplained fever of ≥38.5°C who lived in, worked in, or visited Florac between April 1 and June 30, 2007. Patients were confirmed by a positive Q fever serology test. A cross-sectional survey with a seroprevalence component was carried out in the educational center and surrounding area. A standardized questionnaire on known risk factors for the infection was used and serological testing was carried out on finger prick blood specimens from participants. The veterinary services investigated local herds within a 5-mile radius using polymerase chain reaction and serological tests. RESULTS: One hundred twenty-two people were included in the cross-sectional survey. Eighteen serologically confirmed acute cases were identified, of whom 12 were from the educational center. The statistical analysis showed an independent association between acute infection and living or working near an area where manure had been spread (p = 0.0.042) and male gender (p = 0.022). Frequenting the educational center's canteen was also associated with infection (p = 0.008) among staff and students. The veterinary investigations identified 11 of the 26 tested flocks of goats and sheep as seropositive for Coxiella burnetii, including 2 ovine flocks located northwest of Florac that had high shedding levels of the bacterium. DISCUSSION: The observed excess of cases of Q fever in Florac, an area endemic for this infection, in spring 2007 could be explained by an aerial transmission from infectious ovine flocks situated close to the town. All local herd owners were re-educated about the risks and prevention practices for Q fever.