Epidemiology and Infection

Table of Contents - 2010 - Volume 138, Issue 07  

Cambridge Journals Online - CUP Full-Text Page
Epidemiology and Infection (2010), 138:951-957 Cambridge University Press
Copyright © Cambridge University Press 2009
doi:10.1017/S0950268809990501

For Debate

Dengue

A hypothesis for the 2007 dengue outbreak in Singapore

E. MASSADa1a2a3 c1, F. A. B. COUTINHOa1, S. MAa4 and M. N. BURATTINIa1

a1 School of Medicine, University of São Paulo, São Paulo, Brazil
a2 London School of Hygiene and Tropical Medicine, University of London, UK
a3 Courage Fund of Visiting Professor, National University of Singapore
a4 Ministry of Health, Singapore
Article author query
massad e [PubMed]  [Google Scholar]
coutinho fab [PubMed]  [Google Scholar]
ma s [PubMed]  [Google Scholar]
burattini mn [PubMed]  [Google Scholar]

SUMMARY

A previous mathematical model explaining dengue in Singapore predicted a reasonable outbreak of about 6500 cases for 2006 and a very mild outbreak with about 2000 cases for 2007. However, only 3051 cases were reported in 2006 while more than 7800 were reported in the first 44 weeks of 2007. We hypothesized that the combination of haze with other local sources of particulate matter had a significant impact on mosquito life expectancy, significantly increasing their mortality rate. To test the hypothesis a mathematical model based on the reproduction number of dengue fever and aimed at comparing the impact of several possible alternative control strategies was proposed. This model also aimed at contributing to the understanding of the causes of dengue resurgence in Singapore in the last decade. The model's simulation demonstrated that an increase in mosquito mortality in 2006 and either a reduction in mortality or an increase in the carrying capacity of mosquitoes in 2007 explained the patterned observed in Singapore. Based on the model's simulation we concluded that the fewer than expected number of dengue cases in Singapore in 2006 was caused by an increase in mosquito mortality due to the disproportionate haze affecting the country that year and that particularly favourable environmental conditions in 2007 propitiated mosquitoes with a lower mortality rate, which explains the greater than expected number of dengue cases in 2007. Whether our hypothesis is plausible or not should be debated further.

(Accepted July 05 2009)

(Online publication August 05 2009)

Key Words:Aedes; dengue; haze; models; mosquito mortality

Correspondence:

c1 Author for correspondence: Dr E. Massad, Rua Teodoro Sampaio 115, São Paulo, CEP 05405-000, Brazil. (Email: edmassad@usp.br)

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