As more cases of the mosquito-borne Zika virus spread throughout the Americas, countries attending the Olympics in Rio de Janeiro in August are starting to prepare for the outbreak.

The U.S. Olympic Committee said it is monitoring the situation in Brazil, which is one of the countries hit hardest by the virus. Twenty countries and territories in North and South America are on a travel advisory from the Centers for Disease Control and Prevention.

Zika virus has potentially been linked to the birth defect microcephaly, which can lead to babies being born with smaller heads.

Brazil has seen about 3,448 cases of microcephaly, although more study is needed to confirm the link between Zika and the birth defect, according to the country's Ministry of Health.

The U.S. Olympic Committee is "closely monitoring the situation" and is in constant contact with the International Olympic Committee, Rio officials and the World Health Organization, said spokesman Patrick Sandusky.

"Additionally, we're taking steps to ensure that our delegation and those affiliated with Team USA are aware of the CDC's recommendations regarding travel to Brazil," Sandusky said.

The U.S. isn't the only country worried about the outbreak. Australia's Olympic Committee said on Wednesday that its team medical director is monitoring the situation and warned its athletes about the risks from Zika.

"In Rio the whole of the Australian Olympic Team, athletes and officials, will be issued with mosquito repellent," the committee said.

No country is saying that it is keeping its athletes home from the games.

Currently there is no vaccine or treatment for Zika, which normally causes a fever and rash in infected people.

Rio officials told the BBC on Wednesday that it will hold inspections of Olympic facilities about four months before the games start Aug. 5. During the two-week event, the country will fumigate sites daily, the BBC said.

A rash of new cases were identified in the U.S. on Wednesday, with cases cropping up in New York, Virginia and Minnesota.

The states join Texas, Illinois, New Jersey and Hawaii.

There have been no locally transmitted Zika cases in the U.S., as all the cases have been identified in people returning from affected areas, according to the CDC.