The Centers for Disease Control and Prevention recommends that pregnant women not travel to a number of countries including Fiji and Tonga because of the presence of the mosquito-borne Zika virus, which can cause severe birth defects.

There is no vaccine for Zika, and the CDC says the best way to avoid infection for those who must travel is to take extra precautions to prevent mosquito bites.

The couple is scheduled to visit Tonga on Thursday before returning to Sydney on Friday night for the final days of the Invictus Games, Harry's brainchild and the focus of their tour. The couple will then finish their tour with a four-day visit to New Zealand.

AP