CHICAGO • New research attempting to calculate the risk of the Zika virus at the Olympics in Rio de Janeiro may reassure organisers and many of the more than 500,000 athletes and fans expected to travel to the epicentre of the epidemic.
Controversy about the Games in August has grown as more about the disease becomes known.
The mosquito-borne virus can cause crippling birth defects and, in adults, has been linked to the neurological disorder Guillain-Barre syndrome.
The World Health Organisation, acknowledging the concern, has called a meeting of its Zika experts to evaluate the transmission risk posed by the Olympics.
The debate has played out largely in the absence of models calculating the risk to tourists.
New projections obtained by Reuters suggest the risk is small. One Sao Paulo-based research group predicted the Rio Olympics would result in no more than 15 Zika infections among the foreign visitors expected to attend the event.
The projection echoes that of a separate group of Brazilian scientists, also based at the University of Sao Paulo, in a study published in the journal Epidemiology & Infection in April.
It found the Olympics would result in no more than 16 additional cases of the disease.
Neither study attempted to assess the risk of even a single Olympic traveller carrying the virus back to a vulnerable home country - a central concern of recent calls to reconsider the Games venue.
But a team of United States government epidemiologists calculated that Olympic visitors would account for 0.25 per cent of the total risk of spreading Zika through air travel. That was based on last year's data showing about 240 million people moved to and from areas that now have active transmission.
"Even if the Games were totally shut off and stopped, and the whole thing were cancelled, 99 per cent of that risk is still ongoing," said Dr Martin Cetron, director of global migration and quarantine for the US Centres for Disease Control and Prevention.
Another group of scientists from Brazil's Oswaldo Cruz Foundation recently estimated infections of dengue could range up to 36 cases among Olympic tourists, according to an opinion piece published last week in Memorias Do Instituto Oswaldo Cruz, a peer-reviewed medical journal.
The estimate was based on historical patterns of dengue infection in Rio in August and assumed tourists have the same risk exposure as residents.
The risk of Zika infection, which is transmitted by the same mosquito, would likely be even lower, said Marcelo Gomes, an expert in computational physics at the Oswaldo Cruz Foundation.
Olympic visitors are more likely to stay in areas with greater protection against mosquitoes, including window screens and insecticide, he said in an e-mail, while Aedes aegypti mosquitoes also are less efficient at carrying Zika than dengue.