The Pentagon says 33 members of the US military, including a pregnant woman, are believed to have contracted the mosquito-borne Zika virus overseas.

Air Force Major Ben Sakrisson, a Pentagon spokesman, made the announcement on Wednesday.

One of the military service members was said to be a pregnant woman. Under Pentagon health policies, female service members are allowed to move out of countries where Zika exists.

The Pentagon did not know exactly where the US service members contracted the virus, but they are believed to have been infected outside the continental United States, according to Sakrisson. They began tracking the number of infected personnel earlier this year and found that another six people who have military personnel in their families have also been infected. They do not know how many are still ill or how many have returned to the United States.

A pentagon memo said the mosquito species capable of carrying the virus are likely to be found on 190 US bases in 27 states and 3 territories.

The US Defense Department (DoD) has a Zika Surveillance program and is working with the Centers for Disease Control and Prevention. In May, the DoD provided $1.76 million in extra funding to military laboratories to expand Zika virus surveillance worldwide.

However, the Obama administration warned Congress on Wednesday that money to fight the virus is close to running out, in turn slowing down vaccine development. The news comes as just last week, authorities in Florida reported the first signs of local transmission of the virus in the country. Pregnant women are being warned to stay away from the area.

Health officials warn the mosquitoes are proving harder to eradicate than expected.

CDC poster on mosquito bites prevention

Florida Republican Senator Marco Rubio urged for action on the issue and called the financial situation “inexcusable,” adding that, “Now, I don't like to ascribe motives, but in this case, I have to start wondering whether they are holding back on spending that federal money because they like making this a political issue that they can attack Republicans on."

As of May 18, a total of 544 Americans, including 157 pregnant women, inside 50 states have been diagnosed with Zika, according to CDC statistics. On July 8, the first Zika related death in the country was reported in Utah.

The Zika outbreak was first detected last year in Brazil and since then the virus has been reported in more than 30 countries.

Infections in pregnant women can apparently cause microcephaly, a birth defect marked by small head size that can lead to severe developmental problems in babies. Although the symptoms of the virus are relatively mild and only one in five persons exposed to it becomes ill, those experiencing fever, rash, joint pain, and conjunctivitis (pink eye) have been strongly advised to seek immediate medical care.