Millions of tourists, probably not wearing protective clothing, will descend on Brazils coastal cities during the peak breeding season for mosquitoes
Health experts in Brazil have warned that this years Carnival celebrations could aggravate the spread of the Zika virus, a mosquito-borne disease with possible links to a serious birth defect in babies.
In early February, millions of tourists will descend on Brazils coastal cities, including Rio de Janeiro and Salvador, in the middle of the southern hemisphere summer, the peak breeding season for mosquitoes.
Few visitors are likely to wear protective clothing on the beach or to Carnival street parties, making them vulnerable to insect bites.
I am worried about this large group of susceptible people going to Carnival, said Dr Eurico Arruda, a professor of virology at the University of So Paulo. They will be exposed. It is likely the cases [of Zika] will increase.
Brazilian researchers have linked the outbreak of the Zika virus to a surge in cases of microcephaly, a serious and uncommon condition in which babies are born with smaller than normal heads, causing their brains not to develop properly.
Though the link has not been definitively proven, Brazilian health authorities are confident enough of the connection to recommend that women in Zika-hit areas consider postponing their pregnancies.
A study conducted earlier this week by the Instituto Carlos Chagas, in the southern state of Paran, showed for the first time how the virus passes from mother to foetus through the placenta.
On Wednesday, the Brazilian health ministry announced that the number of cases of microcephaly has continued to rise, with 3,893 reported incidences since October last year. In 2014, there were fewer than 150 cases.
Twenty-one of Brazils 26 states have been affected by the Zika virus, with the epicentre in the north-eastern state of Pernambuco responsible for more than a third of the total number of recorded cases of microcephaly.
In Rio de Janeiro, which receives close to 1 million tourists during Carnival, reported incidences of microcephaly rose 19.4% over the past week, to a total of 166 cases since January 2015. About 4.7 million people attended the citys street parties during last years Carnival.
In an interview with BBC Brasil, Nancy Bellei, the coordinator of the virology clinic at the Brazilian Society of Infectious Diseases, said that the combination of millions on the streets with the outbreak of the Zika virus represented an explosive cocktail that could spread the disease further across the country.
Last Friday, the US federal health agency, the Centers for Disease Control and Prevention (CDC), issued a warning for pregnant women to avoid travelling to Brazil and 15 other Latin American countries that have recorded an outbreak of the disease.
The decision followed the first reported case of microcephaly in the US. A woman who had spent part of her pregnancy in Brazil recently gave birth to a baby with the condition in Hawaii.
Arruda said he agreed with the CDCs caution. We knew nothing about this disease and we were taken by surprise, he said. If I were a pregnant woman, I would not want to be exposed to this.
The virus is transmitted by the Aedes aegypti mosquito, which also carries dengue fever, yellow fever and chikungunya.
At present there is no vaccine and no cure for the Zika virus, though the Brazilian health ministry recently announced the development of a new testing kit for the diseases carried by the mosquito.
In the worst-affected areas, health authorities, sometimes accompanied by soldiers, have been conducting door-to-door searches of residences to clear them of possible mosquito breeding sites, such as standing pools of water.
Elsewhere, Brazilians are being offered cash incentives or being threatened with fines if they fail to ensure their properties are free of mosquitoes.
In Rio de Janeiro, there are also concerns about the possible spread of the disease during the Olympic Games, which begin in August.
Philip Wilkinson, a spokesman for Rio 2016, said that Olympic and Paralympic venues will be inspected on a daily basis to clear possible breeding sites.
With the Olympics due to take place in winter, the colder weather is also expected to limit the number of mosquitoes in the city.