The World Health Organisation (WHO) has called on experts to consider changes to the Rio Olympics schedule.

As the Zika virus spreads, so does international concern about the risk of holding such a major event in the middle of an outbreak.

WHO scientists have been sent to Brazil four times “to gather first-hand data on the current situation and assess the level of risk to the large number of athletes and spectators expected to attend the Olympic Summer Games”, according to a letter from WHO director-general Margaret Chan.

US Senator Jeanne Shaheen has posted Ms Chan's letter online, after asking the Who to evaluate the public health risks of holding the Games in August.

“Given the current level of international concern, I have decided to ask members of the Zika Emergency Committee to examine the risks of holding the Olympic Summer Games as currently scheduled,” Ms Chan said.

The WHO experts will meet “shortly” and post their advice online “immediately”, Ms Chan claimed.

It comes just days after the WHO rejected a call from hundreds of international doctors to change the timing or location of the Rio Games.

But some health experts and advocates say shifting the Games would not really change the risks of Zika spreading globally.

The UN’s official recommendation for women Zika-affected areas is to delay getting pregnant.

They have pushed for “ready access to emergency contraceptive services and counselling” in situations where women have had unprotected sex but do not wish to become pregnant.