The microcephaly epidemic in Brazil generated intense debate regarding its causality, and one hypothesised cause of this epidemic, now recognised as congenital Zika virus syndrome, was the treatment of drinking water tanks with pyriproxyfen to control Aedes aegypti larvae. We present the results of a geographical analysis of the association between the prevalence of microcephaly confirmed by Fenton growth charts and the type of larvicide used in the municipalities that were home to the mothers of the affected newborns in the metropolitan region of Recife in Pernambuco, the state in Brazil where the epidemic was first detected. The overall prevalence of microcephaly was 82 per 10,000 live births in the three municipalities that used the larvicide Bti (Bacillus thuringiensis israelensis) instead of pyriproxyfen, and 69 per 10,000 live births in the eleven municipalities that used pyriproxyfen. The difference was not statistically significant. Our results show that the prevalence of microcephaly was not higher in the areas in which pyriproxyfen was used. In this ecological approach, there was no evidence of a correlation between the use of pyriproxyfen in the municipalities and the microcephaly epidemic.

Um estudo de caso-controle foi conduzido no Estado de Pernambuco, Brasil, para identificar fatores de risco para morte por tétano. As informações foram obtidas dos prontuários médicos de 152 casos e 152 controles, admitidos na Unidade de Tétano do Hospital Universitário Oswaldo Cruz, na cidade do Recife, de 1990 a 1995. As variáveis foram agrupadas em três diferentes conjuntos. Foram estimados os "odds ratios" brutos e ajustados, o intervalo de confiança de 95% e o valor de "p". As variáveis selecionadas na análise multivariada em cada conjunto, foram controladas para os efeitos daquelas selecionadas nos demais. Todos os fatores relacionados à progressão da doença - período de incubação, tempo decorrido entre o primeiro sintoma de tétano e a admissão no hospital, e período de progressão - mostraram uma associação estatisticamente significante com morte por tétano. De modo semelhante, o segundo conjunto de variáveis - sinais e/ou sintomas que ocorreram à admissão ou nas primeiras 24 horas: espasmos, rigidez de nuca, sinais e sintomas respiratórios - bem como as variáveis do terceiro conjunto - insuficiência respiratória que necessitou de respiração artificial foram associadas com morte por tétano, mesmo quando ajustadas com os efeitos das demais variáveis.

A case-control study was conducted to identify risk factors for death from tetanus in the State of Pernambuco, Brazil. Information was obtained from medical records of 152 cases and 152 controls, admitted to the tetanus unit in the State University Hospital, in Recife, from 1990 to 1995. Variables were grouped in three different sets. Crude and adjusted odds ratios, p-values and 95% confidence intervals were estimated. Variables selected in the multivariate analysis in each set were controlled for the effect of those selected in the others. All factors related to the disease progression - incubation period, time elapsed between the occurrence of the first tetanus symptom and admission, and period of onset - showed a statistically significant association with death from tetanus. Similarly, signs and/or symptoms occurring on admission or in the following 24 hours (second set): reflex spasms, neck stiffness, respiratory signs/symptoms and respiratory failure requiring artificial ventilation (third set) were associated with death from tetanus even when adjusted for the effect of the others.