How Utah Zika Infection Was Transmitted Remains Mystery

As of July 13, more than 1,300 confirmed cases of Zika virus infection in the continental United States and more than 2,900 cases in the U.S. territories had been reported to the CDC’s ArboNET(www.cdc.gov) arboviral surveillance system.

In addition, the CDC released a Morbidity and Mortality Weekly Report (MMWR)(www.cdc.gov) on July 13 that said travel to Brazil for the upcoming 2016 Olympic Games, as well as for the Paralympic Games in September, should not, in most instances, “pose a unique or substantive risk for mosquito-borne transmission of Zika virus in excess of that posed by non-games travel.”

And the Zika narrative continues to unfold, with just this past week marking a couple Zika firsts: the first case of Zika virus infection not transmitted via sexual contact or mosquito bites and the first case of confirmed female-to-male sexual transmission.

Utah Zika Case Raises Questions

The Utah Department of Health (UDOH) and Salt Lake County Health Department announced(udohnews.blogspot.com) on July 18 a new case of confirmed Zika virus infection that wasn’t attributed to sex with someone infected with the disease, was not transmitted by a pregnant woman to her child and could not be tied to a bite from an infected Aedes mosquito.

The CDC said in a media statement(www.cdc.gov) that this person was a “family contact” who had helped care for another Utah resident, an elderly man who had died in late June from unknown causes but who had been infected with Zika after traveling to an area with active transmission of the disease. The CDC confirmed Zika infection in both patients, but the method of transmission between the two remains a mystery. The patient in this new case has since recovered completely from the infection.

“The new case in Utah is a surprise, showing that we still have more to learn about Zika,” said Erin Staples, M.D., Ph.D., CDC medical epidemiologist, in the media statement. “Fortunately, the patient recovered quickly, and from what we have seen with more than 1,300 travel-associated cases of Zika in the continental United States and Hawaii, nonsexual spread from one person to another does not appear to be common.”

Also of note, according to the agency, was the fact that the deceased patient had an unprecedented amount of Zika virus in his blood — more than 100,000 times higher than viral loads seen in other samples from infected patients.

The CDC has sent an emergency response team to Utah to assist state and local public health disease control specialists in the investigation. According to the agency, this process will include additional interviews with and laboratory testing of family members and health care professionals who may have had contact with the patient who died, as well as trapping mosquitoes and assessing the risk of local spread via that route.

Female-to-Male Case

The CDC released an MMWR on July 15(www.cdc.gov) that reports on an investigation by the New York Department of Health and Mental Hygiene (DOHMH) into the first documented case of female-to-male sexual transmission of Zika virus. All previously reported cases of sexually transmitted Zika virus infection have been spread from men to their sexual partners.

This patient was identified as a nonpregnant woman in her 20s who said she had engaged in a single episode of condomless vaginal intercourse with a male partner the day she returned to New York City after traveling to an area with active Zika transmission. She became symptomatic a day later and visited her primary care physician a couple of days after that, where blood and urine samples were collected. Zika virus RNA was detected in both serum and urine using real-time reverse transcription-polymerase chain reaction (rRT-PCR) at the DOHMH Public Health Laboratory.

Seven days after sexual intercourse, the woman’s male partner, who had not traveled outside the United States and also was in his 20s, developed fever, a maculopapular rash, joint pain and conjunctivitis. Three days later, the man visited the same primary care physician who had diagnosed Zika virus infection in the female patient and blood and urine were collected. Zika virus RNA was detected in his urine but not serum using rRT-PCR testing at the DOHMH laboratory. The CDC Arbovirus Disease Branch confirmed all rRT-PCR results for both partners.

The CDC said the timing and sequence of events support female-to-male Zika virus transmission through condomless vaginal intercourse, with the virus present in either vaginal fluids or menstrual blood being transmitted via her male partner’s urethral mucosa or undetected abrasions on his penis.

In a related media statement,(www.cdc.gov) the CDC said it’s currently updating recommendations for sexually active people.

The agency previously has recommended that all pregnant women who have a sexual partner who has traveled to or resides in an area with active Zika virus transmission should use barrier methods every time they have sex or they should not have sex during the pregnancy.

And although no cases of woman-to-woman Zika transmission have been reported, these recommendations now also apply to female sexual partners of pregnant women.

Olympics Risk Assessment

In another MMWR on July 13,(www.cdc.gov) the CDC conducted a risk assessment of how travel to and from the 2016 Olympic Games in August, as well as to the Paralympic Games the following month, would affect Zika transmission. Researchers said that because it will be winter in host city Rio de Janeiro during the games, mosquito-borne transmission of Zika virus is predicted to be low.

Nineteen of the 206 countries participating in the event have no evidence of ongoing or previous Zika virus transmission but do have environments and population conditions that could support mosquito-borne Zika transmission if the disease was introduced by a traveler back from the Olympics. For 15 of these 19 participating countries, travel to Rio during the games isn’t projected to substantially increase the risk of Zika importation more than their respective baseline levels of air travel.

However, because Chad, Djibouti, Eritrea and Yemen don’t normally offer many travel options to other countries with active Zika virus transmission, travelers back from the games to these countries do pose a heightened risk of mosquito-borne transmission of the virus. But it should also be noted that these four countries will only be represented by a projected combined total of 19 athletes (plus a delegation of about 60 people) — a miniscule fraction of the 350,000 to 500,000 visitors expected to attend the games — so the absolute risk of transmission back home is small.

Source: AAFP