Zika Transmitted by Man with No Symptoms

zika test positive
Science & Medicine

On August 26, 2016, health officials announced the first case of Zika spread through sex by a man with no symptoms of the virus. Zika has been sexually transmitted in 21 other cases, but those infections were passed on by someone with symptoms of the disease. [1]

Read: Zika Virus Is “Scarier than the CDC Initially Thought”

According to health officials, the man, a Maryland resident, had traveled to the Dominican Republic, which is in the midst of a Zika outbreak. The patient didn’t get sick during the trip or when he returned to the U.S. However, his sex partner, who hadn’t traveled, did get sick.

In the majority of cases, the Zika virus is transmitted through mosquito bites. Most of those who are infected never get sick. People who do get sick generally have mild symptoms that include fever, rash, and joint pain.

Pregnant women who become infected with the disease can give birth to infants with severe birth defects, including microcephaly.


It’s incredibly rare that Zika is spread by someone without any symptoms. Doctors theorize it may occur if an infected person has smaller amounts of the virus in their blood and bodily fluids, and is less infectious.

The Centers for Disease Control (CDC) advises couples to use condoms for two months after a partner without symptoms has returned from a Zika outbreak area, if the woman is of childbearing age. Men who have symptoms are advised to use condoms for at least six months.

Read: Zika May Be Spread Through Oral Sex

The CDC’s Dr. John T. Brooks said the Maryland case is extraordinarily rare and the current guidance won’t change as a result.

The only other documented case of the virus being spread by an individual with no symptoms occurred in France. And in that case, health officials can’t be sure the woman caught the virus through sexual activity. Brooks explained:

“She didn’t develop Zika until about 40 days after she got home, so it’s possible she was infected via sex, but it’s also possible that it was a very delayed incubation from a mosquito bite.” [2]

However, Brooks said the Maryland case “illustrates the need for careful precautions when visiting an area where Zika is circulating.”

He continued:

“Be sure to wear insect repellent and appropriate clothing, and use CDC guidance on safe sex when you return. This is especially critical for women who are pregnant or trying to conceive and their partners.

Pregnant couples need to defer unprotected sexual contact for the entire pregnancy, even if the exposed partner never develops symptoms of Zika. A few months of precautions can prevent devastating lifelong defects for the developing fetus.” [2]


[1] The Associated Press

[2] CNN NOTE: This is CDC, not CNN, and does not contain the referenced text.