Football fever: dengue in Brazil

The 2014 FIFA World Cup could have fans reaching fever pitch for reasons other than football: the event also coincides with the country's seasonal spike in dengue virus cases, an Oxford scientist has warned.

Half a million spectators are expected to flock to Brazil for next year's World Cup, matches for which will be played in a number of dengue high-risk venues including the cities of Fortaleza, Natal and Salvador in the country's northeast.

Dengue is a mosquito-borne viral haemorrhagic fever that can cause a severe flu-like febrile illness; it can also be fatal, and there are no vaccines or anti-viral agents with which to prevent or treat infection. Each year Brazil records over 6000 cases of the disease and about 500 deaths.

Distribution maps charting the seasonal variation in dengue rates around the country show that, although the main dengue season will have passed in the locations of nine of the main stadia by the time when matches are scheduled to be played there, the risk will still be close to its peak around the three other venues in the northeast.

Based on this finding, Oxford University epidemiologist Simon Hay, writing in Nature this week, is urging the Brazilian authorities to implement aggressive strategies to control the numbers of the Aedes aegypti mosquitoes responsible for spreading the infection.

These mosquitoes thrive in places where stagnant water accumulates, such as around refuse tips bordering towns and cities. Evidence from elsewhere around the globe shows that clearing up these sources, as well as fogging with insecticides, can heavily suppress Aedes aegypti numbers, both of which Hay urges the Brazilians to consider.

He also highlights another spectre looming on the horizon: the half a million visiting fans may, ironically, bring their own strains of dengue with them, introducing variants of the agent that are currently rare in Brazil. That immunity to these imported strains could be low among locals, and the assembly in the country of large numbers of non-immune visitors, are both factors that could fuel outbreaks.

"I don't want to dissuade anyone from going to the world cup, nor to single out Brazil, which is just one of more than 100 countries worldwide battling dengue.

My aim is to inform unwary spectators about the risk and how they can protect themselves," Hay says in concluding his Nature commentary, adding "Come on England," for good measure...