Dengue fever early warning system makes predictions for Brazil World Cup

For the first time, a team of European scientists has developed an early warning system that estimates the chances of outbreaks of dengue fever in the 553 microregions of Brazil during the soccer World Cup.

The multidisciplinary team, comprising climate scientists, public health specialists and mathematical modellers, describes the new system in a study published in The Lancet Infectious Diseases.

Dengue is a fast-spreading tropical viral infection that is transmitted from human to human via mosquitoes. Dengue fever can be life-threatening, and there are currently no licensed vaccines or treatments.

With more than 7 million reported between 2000 and 2013, Brazil has recorded more cases of dengue fever this century than any other country worldwide.

For the study, the team looked at rain and temperature data spanning a 30-year period. They also took into account population density and altitude data.

They describe how they assessed the past performance of the forecasting system using "observed dengue incidence rates for June, 2000-2013, and identified optimum trigger alert thresholds for scenarios of medium-risk and high-risk of dengue."

Co-author David Stephenson, a professor in the mathematics department at Exeter University in the UK, says:

"Similar to many infectious diseases, the risk of dengue dynamically depends on local climate and so varies in time and space. Our study uses a state-of-the-art statistical model to combine operational climate forecasts with socioeconomic factors to make probabilistic warnings of dengue."

High alert dengue warnings for three Brazil World Cup venues

More than a million spectators are expected to travel among the 12 cities in Brazil where the World Cup matches are taking place from June 12th to July 13th, 2014.

The study finds the risk of dengue fever outbreaks for June 2014 is high enough to warrant "high alert" warnings in three north-eastern Brazil World Cup venues: Natal, Fortaleza and Recife.

More than a million spectators are expected to travel among the 12 cities in Brazil where the soccer World Cup matches are taking place in July.

However, it finds dengue risk for the period is likely to be low in five host cities: Brasília, Cuiabá, Curitiba, Porto Alegre and São Paulo.

And in Rio de Janeiro, Belo Horizonte, Salvador, and Manaus, the study suggests the risk of dengue fever outbreak is medium.

While there have been dramatic headlines about dengue fever in Brazil during the World Cup, they stemmed from estimates based solely on averages of past dengue cases.

But, as lead author Dr. Rachel Lowe, of the Catalan Institute of Climate Sciences in Barcelona, Spain, explains: "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."

She adds that the ability to give timely dengue early warnings at the microregion level 3 months in advance gives the Brazilian authorities invaluable information for reducing or containing an epidemic. They will have "time to combat mosquito populations in those cities with a greater chance of dengue outbreaks," she notes.

In April 2013, experts claimed that the annual worldwide number of dengue cases is likely three times higher than current estimates from the World Health Organization. Researchers from the University of Oxford and the Wellcome Trust in the UK calculated the actual number to be nearer 390 million people infected with the dengue virus annually.