a1 Maccabi Healthcare Services, Tel Aviv, Israel
a2 Tel Aviv University, Department of Family Medicine, Sackler Faculty of Medicine, Tel Aviv, Israel
a3 Tel Aviv University School of Public Health, Department of Health Promotion, Sackler Faculty of Medicine, Tel Aviv, Israel
a4 Ben-Gurion University, Faculty of Medicine, Beer-Sheva, Israel
a5 Tel Aviv University, Department of Statistics and Operations Research, Tel Aviv, Israel
Proposed measures to contain pandemic influenza include school closure, although the effectiveness of this has not been investigated. We examined the effect of a nationwide elementary school strike in Israel in 2000 on the incidence of influenza-like illness. In this historical observational study of 1·7 million members of a preferred provider organization, we analysed diagnoses from primary-care visits during the winter months in 1998–2002. We calculated the weekly ratio of influenza-like diagnoses to non-respiratory diagnoses, and fitted regression models for school-aged children, children's household members, and all other individuals aged >12 years. For each population the steepest drop in the ratio of influenza-like diagnoses to non-respiratory diagnoses occurred in the strike year 2 weeks after the start of the strike. The changes in the weekly ratio of influenza-like diagnoses to non-respiratory diagnoses were statistically significant (P=0·0074) for school children for the strike year compared to other years. A smaller decrease was also seen for the adults with no school-aged children in 1999 (P=0·037). The Chanukah holiday had a negative impact on the ratio for school-aged children in 1998, 1999 and 2001 (P=0·008, 0·006 and 0·045, respectively) and was statistically significant for both adult groups in 1999 and for adults with no school-aged children in 2001. School closure should be considered part of the containment strategy in an influenza pandemic.
(Accepted March 05 2009)
(Online publication April 07 2009)