SCOTLAND'S leading health experts have warned athletes to 'think twice' before going to the Rio Olympics - or even pull out of the games altogether - as fears grow about the Zika virus, which has triggered a world health emergency.

Devi Sridhar, professor of global public health at the University of Edinburgh Medical School, said athletes should 'think twice' about attending after the World Health Organization (WHO) rejected a call to move or postpone the Games due to the outbreak of the mosquito-borne disease in Brazil.

Hugh Pennington, one of Scotland's foremost experts on viruses, also told the Sunday Herald that athletic governing bodies, from competing nations, should threaten to pull out of this summer's Olympics unless the Brazilian authorities can guarantee that they will be able to control the mosquito population.

WHO said moving or postponing the Games would "not significantly alter" the spread of the virus, which can lead to babies being born with underdeveloped brains, following an open letter to the global health authority from more than 100 leading scientists who said new findings about Zika made it "unethical" for the Games to go ahead.

Sridhar says that Zika should be seen as a "huge problem" for athletes competing in Brazil - just weeks after she told The Sunday Herald that Zika would definitely spread to Europe due to travel and sexual contact.

Sridhar, who has worked with a number of UN agencies and Ministries of Health in emerging and developing countries, said that male athletes in particular who are thinking about having children should weigh up the risks of going to the Brazilian capital for the Games.

She also suggested that individual nations should also review whether it will be safe to send teams of sportsmen and women to Brazil, where the country's health ministry registered 91,387 likely cases of the Zika virus and where the number of babies born with Zika-linked defects stood at 4,908 in April.

Pennington, an emeritus professor of bacteriology at the University of Aberdeen, said that nations should not commit to sending teams to Brazil until independent international public health experts had given the all-clear to the spaces where athletes will be accommodated during the games, which take place from August 5 to 21.

He said: "The only thing that really matters is the control of the mosquitoes. The Olympics are a special case with the athletes living in purpose built villages, so it boils down to whether the Brazilian authorities can offer a safe environment.

"National athletic bodies could say they are not going to send athletes until there are guarantees about control measures for mosquitoes. They could ask for a clean bill of health to be given after international health inspectors have been sent in.

"If they wanted to do that it would be a reasonable thing to ask for and it would put pressure on the Brazilians to do that now. With that hidden cosh, they could ask for really good solid evidence to be provided."

Meanwhile, Sridhar said that although she was not fully convinced by the calls to postpone the games in the letter signed by 150 international scientists, doctors and medical ethicists from such institutions as Oxford University and Harvard and Yale universities in the US, athletes should seriously consider the risks of going to Rio.

She said: "It's a hard one and the health community is split on this. On the one hand you are more likely to get food poisoning, vomiting or diarrhoea, but you definitely have to think before sending a team.

"It's important not to overblow it, but the debate needs to happen and we need to have that conversation. Athletes also need to be aware that there is a huge problem and this has to be put on their radar."

Sridhar also suggested that any decision about whether the Olympics should go-ahead and whether individual nations should compete should be influenced be concerns that the Zika outbreak could turn out to be worse than initially thought.

She added: "Zika is here to stay, but the question is if we postpone it, will it get any better in six months time.

"There are a lot of people sitting on the fence about it, but we all know that models about the scale of a risk can be flawed.

"I'd say that people should take proper precautions and if there are male athletes who are thinking about having children for example then they should think twice because of the sexual transmission risk issue."

Sridhar previously claimed that a major problem in responding to the Ebola outbreak had been a failure to share information within the research and public health community, leading to problems with treating the virus and preventing it spreading.

She also warned there would be more UK cases of Zika than of Ebola, which saw Scottish nurse Pauline Cafferkey treated in hospitals in Glasgow and London after contracting the virus in Sierra Leone.

Meanwhile, the International Olympic Committee (IOC) has said it sees no reason to delay or move the Games because of Zika. The outbreak began in Brazil a year ago, but now more than 60 countries and territories have continuing transmission.