Analyses by researchers have shown 100% genetic correlation between the form of the virus present in a man who contracted the virus in Brazil and that of a woman who had never travelled in the epidemic area, but who had sexual relations with him.
The researchers are from Inserm, the Paris Public Hospitals, Aix-Marseille University, and the National Reference Centre for Arboviruses.
The ZIKA virus, a member of the Flavivirus family, is almost exclusively transmitted to humans by Aedes mosquitoes.
Although Zika infection usually causes mild symptoms, it can be responsible for severe neurological complications, particularly in the infant of a woman infected while pregnant.
For the first time, and to take things further, French researchers have been able to culture the infecting virus from two people seeking a consultation for suspected ZIKA infection.
Specimens of urine, saliva and blood were taken from a man who returned from Brazil, and had contracted the virus there.
The same specimens were taken from a sick woman who had sexual relations with this man, but who had never travelled to an epidemic area.
While the virus was detected in the urine and saliva of the woman, analysis of the specimens showed that it was absent from the blood and saliva of the man, making it unlikely that transmission occurred by these routes.
The researchers then tested his semen for the virus, and detected high viral loads at 15 days and at three weeks after the patient’s return from Brazil (approximately 300 million copies/ml).
The virus from both persons was individually sequenced (using a saliva sample from the woman and a semen sample from the man) for genetic analysis.
Examination showed 100% correlation between the two genetic sequences. Apart from four mutations, all of them “synonymous,” the nucleotide sequences both encoded an identical form of the virus.
“Our work confirms, using molecular analyses, that sexual transmission of the ZIKA virus exists, and should be taken into consideration when making recommendations, due to its persistence in the semen several weeks after infection. The period for which men should systematically have protected sexual relations (even oral) needs to be defined,” explains researcher, Yazdan Yazdanpanah.
And in another similar research, scientists at the Centers for Disease Control and Prevention (CDC) have concluded, after careful review of existing evidence, that Zika virus is a cause of microcephaly and other severe fetal brain defects.
Microcephaly is a rare neurological condition in which an infant’s head is significantly smaller than the heads of other children of the same age and sex. Sometimes detected at birth, microcephaly usually is the result of the brain developing abnormally in the womb or not growing as it should after birth.
“This study marks a turning point in the Zika outbreak. It is now clear that the virus causes microcephaly. We are also launching further studies to determine whether children who have microcephaly born to mothers infected by the Zika virus is the tip of the iceberg of what we could see in damaging effects on the brain and other developmental problems,” said Tom Frieden, M.D., M.P.H., director of the CDC.
“We’ve now confirmed what mounting evidence has suggested, affirming our early guidance to pregnant women and their partners to take steps to avoid Zika infection and to health care professionals who are talking to patients every day.”
The report notes that no single piece of evidence provides conclusive proof that Zika virus infection is a cause of microcephaly and other fetal brain defects. Rather, increasing evidence from a number of recently published studies and a careful evaluation using established scientific criteria supports the authors’ conclusions.
The finding that Zika virus infection can cause microcephaly and other severe fetal brain defects means that a woman who is infected with Zika during pregnancy has an increased risk of having a baby with these health problems.
It does not mean, however, that all women who have Zika virus infection during pregnancy will have babies with problems. As has been seen during the current Zika outbreak, some infected women have delivered babies that appear to be healthy.
Establishing this causal relationship between Zika and fetal brain defects is an important step in driving additional prevention efforts, focusing research activities, and reinforcing the need for direct communication about the risks of Zika, CDC researchers said.
They said while one important question about causality has been answered, many questions remain.
Answering these will be the focus of ongoing research to help improve prevention efforts, which ultimately may help reduce the effects of Zika virus infection during pregnancy.
At this time, CDC is not changing its current guidance as a result of this finding. Pregnant women should continue to avoid travel to areas where Zika is actively spreading.
If a pregnant woman travels to or lives in an area with active Zika virus transmission, she should talk with her healthcare provider and strictly follow steps to prevent mosquito bites and to prevent sexual transmission of Zika virus.