Already grappling with construction delays, budget cuts, pollution and a sinking economy, Rio 2016 organizers now face a health alert as they prepare for this summer's Olympic Games.

Brazil is battling to contain an outbreak of the Zika virus, which has been linked to birth defects and the paralysis-causing Guillain-Barre syndrome.

The US Centers for Disease Control and Prevention has warned pregnant women against traveling to Brazil and other countries where the virus is present.

Officials in Rio said measures were being taken to prevent the accumulation of stagnant water, which is a breeding ground for the Aedes aegypti mosquito that carries the virus.

"Rio 2016 will continue to monitor the issue closely and follow the guidance of the ministry of health," the organizing committee said in a statement.

The Olympics will be held from Aug 5-21, during Brazil's dry season, and officials say this means the mosquitoes will be less prevalent.

The Zika virus outbreak also comes as Rio prepares for its annual Carnival celebration, which begins on Feb 5.

Brazil is mobilizing 220,000 troops to curb the spread of the Zika virus. The troops will be dispatched to states most affected by the disease following warnings by the country's health officials that Brazil was "losing the battle" against the mosquitoes.

According to Nancy Bellei, coordinator of clinical virology at Brazil's infectious diseases institute, current high humidity means tourists face a greater risk.

"This is the worst time to deal with an epidemic of a virus we know very little about," she said. "The government is trying to raise awareness and fight the mosquitoes but we won't achieve control in the short term under the current circumstances."

Bellei added that the virus could easily spread to other countries by infected visitors.