Brazil has been urged to act aggressively to head off a risk from dengue fever at next year's soccer World Cup.
The risk from the dangerous mosquito-borne virus will be greatest at matches played in three northeastern cities, Fortaleza, Natal and Salvador, said Simon Hay, a fellow at Oxford University.
In other cities, the dengue season is likely to have peaked before the June 12-July 13 tournament, he said.
"Unfortunately, the risk remains high during these months in the northeast," Hay said in a commentary in the prestigious scientific journal Nature.
"The Brazilian authorities should implement aggressive vector control in April and May, particularly around the northern stadiums, to decrease the number of dengue-transmitting mosquitoes.
"They can target adult Aedes mosquitoes through fogging (the use of aerosol formulations of insecticides that disperse efficiently) and can interrupt breeding by clearing sites at which the mosquitoes lay their eggs -- water collected in discarded rubbish, for example."
Dengue, induced by a virus transmitted in the mosquito's bite, can produce a flu-like illness that may need hospitalisation. Sometimes a lethal complication, severe dengue, can develop. There is no vaccine.
People heading to areas where dengue is a problem should use insect repellents, wear clothing that covers the arms and legs, especially during early morning and late afternoon, and choose accommodation with screened windows, doors and air conditioning, said Hay.
He also pointed to a theoretical risk for Brazilians -- that outsiders bring in types of the dengue virus against which the host population has low immunity.
Health watchdogs in all countries with dengue can contribute to the solution by using online monitoring tools, such as DengueMap and Google's Dengue Trends, which records outbreaks of the disease, he said.
On November 20, Brazil said at least 573 people had died from dengue so far this year, compared with 292 in 2012 and 472 in 2011.
The highest death toll was in the southeastern state of Minas Gerais (116), followed by Sao Paulo state (72), Goias (58), Ceara in the northeast (54) and Rio de Janeiro state (48).
The total number of serious cases reported so far this year reached 6,566, leading authorities in 157 cities to declare a state of alert. They include Salvador and Fortaleza, as well as Rio de Janeiro and Manaus.
The UN's World Health Organisation (WHO) says that dengue is spreading, helped by travel and the globalisation of trade, and 40 percent of the world's population are now at risk from it.
Between 50 and 100 million dengue infections occur each year in more than 100 countries, according to the WHO website. In 1970, the disease was endemic in just nine countries.