Researchers have developed a novel early warning system to assess the likelihood of a dengue epidemic in Brazil during the World Cup, and they indicate that the highest risk for an outbreak is in three northeastern cities that will be hosting some of the matches this year.
More cases of dengue fever were reported in Brazil this century than anywhere else in the world, with more than 7 million cases occurring between 2000 and 2013, according to Rachel Lowe, PhD, of the Catalan Institute of Climate Sciences in Barcelona, Spain, and colleagues.
“Recent concerns about dengue fever in Brazil during the World Cup have made dramatic headlines, but these estimates have been based solely on averages of past dengue cases,” Lowe said in a press release. “The possibility of a large dengue fever outbreak during the World Cup, capable of infecting visitors and spreading dengue back to their country of origin, depends on a combination of many factors, including large numbers of mosquitoes, a susceptible population, and a high rate of mosquito-human contact.”
Lowe and colleagues developed a forecasting model to predict the risk of a dengue epidemic in all 553 microregions of Brazil and assigned risk-level estimates for each of the 12 cities in which World Cup matches will be played, starting on June 12. The model, based on a Bayesian algorithm, used real-time seasonal climate forecasts from numerous sources and allowed the researchers to make predictions up to 3 months in advance.
“Our aim was to take the available evidence on real-time seasonal rainfall and temperature forecasts, transmission dynamics, and social and environmental variables, and combine it with the latest in mapping and mathematical modelling to produce robust risk estimates for the 12 host cities where matches will be played,” Lowe said.
The early warning system indicated that there is little risk for dengue outbreaks in the southern and central host cities of Brasília, Cuiabá, Curitiba, Porto Alegre and São Paulo. Medium-risk alerts were assigned to Rio de Janeiro, Belo Horizonte, Salvador and Manaus. The northeastern cities of Recife, Fortaleza and Natal appear to be at the highest risk, although the risk is still relatively low.
According to Lowe, results from the forecasting model should be used to direct disease prevention and control strategies.
“An effective early warning system for dengue that takes into account multiple factors, including real-time climate forecasts, allows the concentration of vector control efforts and health center provisions to those areas most at risk, 3 months in advance,” Lowe told Infectious Disease News. “This may be useful, not only ahead of major global events, but also before the peak dengue season each year, to control or contain potentially explosive dengue epidemics.”
In a related editorial, David Harley, PhD, and Elvina Viennet, PhD, of the National Centre for Epidemiology and Population Health at the Australian National University, wrote that most spectators who infect mosquitos with dengue upon their return home from the World Cup live in dengue endemic countries anyway and would have little effect on the local epidemiology. Only a few will return to tropical areas where Aedes aegypti mosquitos are present but dengue incidence is low.
“The FIFA World Cup is a major sporting event,” they wrote. “The results for dengue epidemiology, and on the football pitch, will be fascinating. We await both outcomes with interest.” – John Schoen
For more information:
Harley D. Lancet Infect Dis. 2014;doi:10.1016/S1473-3099(14)70769-9.
Lowe R. Lancet Infect Dis. 2014;doi:10.1016/S1473-3099(14)70781-9.
Disclosure: Lowe reports no relevant financial disclosures.