The Centers for Disease Control and Prevention has recommended expanded testing, especially for pregnant women, as part of a new guidance to prevent the transmission of the Zika virus that causes serious birth defects.
The updated CDC guidance expands the Zika-specific blood testing for a longer period, up to 14 days, in pregnant women with symptoms. It also advises pregnant women with possible Zika exposure, but no symptoms, to get this kind of testing.
Although the CDC said the mosquito-borne virus outbreak already has affected most of South and Central America and Mexico in North America, no local mosquito-borne Zika virus cases have been reported in the U.S.
“As of July 20, 2016, there have been a total of 1,404 cases of Zika virus reported in the United States,”
CDC spokesman Benjamin N. Haynes said, adding that all but one of them were caused by people getting infected by traveling to areas where the carrier type of mosquitoes are prevalent. One person in the U.S. is known to have acquired the virus from a laboratory.
Until now, scientists thought that if a person becomes sick after being infected with Zika, the virus stays in the person’s blood for about a week after symptoms started. “So the first week of illness was thought to be the best time to find evidence of the virus in blood using a Zika-specific test,” the CDC said.
A significant problem is that many people infected with Zika won’t have symptoms or will have only mild symptoms. Those people may not go to a health facility. The most common symptoms of the Zika virus are fever, rash, joint pain and conjunctivitis (inflammation in the eyes). Other symptoms include muscle pain and headache.
Haynes said: “Four out of five people infected with Zika virus don’t even know they have the disease. The sickness is usually mild with symptoms lasting for several days to a week. People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika.”
Although the symptoms for adults may be mild, the birth defects can be horrendous. “In a published review of existing evidence, CDC scientists concluded that Zika virus infection during pregnancy can cause microcephaly and other severe fetal brain defects,” Haynes said.
Microcephaly is a medical condition that keeps the brain from developing properly. It can result in a smaller than normal head. It also can cause intellectual disability, poor motor function, poor speech, abnormal facial features, seizures and dwarfism. “Scientists continue to study the full range of other potential health problems that Zika virus infection during pregnancy may cause,”
There is a different test for people who see a doctor more than a week after symptoms start; that is, after the virus has cleared from the blood. It can also be used for those who were possibly exposed to Zika, but never developed symptoms.
The test looks for evidence that the body is fighting a virus in the family of viruses that includes Zika. The results of this test are more difficult to interpret because the body’s reaction to Zika virus can resemble the reaction to similar viruses; therefore, this test may not provide a definitive diagnosis.
The CDC said new information has indicated that some infected pregnant women can have evidence of Zika in their blood for longer than the previously recommended seven-day window for testing after symptoms begin. Even pregnant women without symptoms can have evidence of the virus in their blood and urine.
Those are the reasons CDC expanded its testing recommendations up to 14 days. Furthermore, if a pregnant woman tests positive with the less-specific test after the 14-day window, the CDC said the Zika-specific blood test can then be used to “potentially provide a definitive diagnosis for” her. Such a diagnosis could “help direct medical care.”
“This expanded guidance is based on a recently reported case of female-to-male sexual transmission in New York City and limited human and non-human primate data indicating Zika virus RNA can be detected in vaginal secretions,” the CDC said.
This research “expands CDC’s definition of sexual exposure to Zika to include sex without a barrier method (including male or female condoms) with any person - male or female - who has traveled to or lives in an area with Zika.”
The new guidance did note, though, that “transmission of Zika from a woman to her sex partners is believed to be uncommon and is unlikely to result in serious side effects.”