Amid growing fears and increasing numbers of people infected by the mosquito-transmitted virus Zika, the World Health Organization (WHO) delivered a positive forecast for the Rio Summer Games on Friday.

"Brazil is going to have a fantastic Olympics, and it's going to be a successful Olympics. And the world is going to go there," Bruce Aylward, a senior official of WHO's Zika response team, said at a news conference.

"I just wish I was going there, but there's not going to be a lot of problems there by then, so I'll be somewhere else," he told reporters, adding that the mosquito population is expected to drop off in Rio by the start of the games.

He noted that the Olympic venues in Rio de Janeiro were located in a relatively confined area, which makes it easier to control the local mosquito population.

Aylward also said there is a "probability" that the Zika virus will have "gone through" a large portion of the country's population by then, so many Brazilians might have developed an immunity to the disease by the start of the August 5-21 games.

Authorities in Brazil estimated that there are up to 1.5 million people who have been infected in the country, but they reportedly stopped counting due to the magnitude of the outbreak.

Link still 'months off'

Despite an accumulation of strong evidence over the past few weeks, researchers may still need months to prove the relation between the Zika virus and microcephaly, WHO also announced on Friday.

Babies whose mothers are infected with the virus at the start of their pregnancies are at a higher risk of developing the debilitating disorder, Aylward said. Scientists, therefore, still need between four to six months to prove the link after collecting data from more newborns.

However, Aylward said it may only take weeks to establish a link between Zika and Guillian-Barre syndrome, a neurological disorder which causes muscle weakness.

The virus is transmitted by mosquitoes, but there have been a small number of cases of sexual transmission through semen.

Men and women traveling to outbreak regions should practice safer sex for one month after returning home, the WHO advised this week. Even Pope Francis showed signs of softening his view on contraceptives, in light of the Zika outbreak.

The virus has currently spread to 36 countries, most of them in the Americas, and usually causes only mild symptoms like fever in those who have been infected. WHO declared an international public health emergency over Zika earlier this month.

rs/jm (AP, dpa, Reuters)