Zika can remain in semen for six months

The Zika virus has been detected in the semen of a man six months after the onset of infection.

Researchers from the Spallanzani Institute for Infectious Diseases in Rome first detected the virus in the urine, saliva and semen of an Italian man who had been visiting Haiti, 91 days after the first symptoms had been observed. Further testing showed that it remained present in his semen at 134 days and was still detectable at day 181.

The researchers explain that the finding confirms that the virus can replicate in the male genital tract and presents 'a prolonged potential risk for sexual transmission' than was previously thought.

The longest period that the Zika virus has been detected in semen after the onset of infection was previously reported as 93 days, in a 27-year old French man. Current guidelines by Public Health England (see BioNews 840) recommend that men infected with the Zika virus should practice safe sex using condoms for six months. The Human Fertilisation and Embryology Authority (HFEA) recommends that people returning from Zika-virus prone regions should not undergo fertility treatment, donate sperm or eggs, or try to conceive for eight weeks, recently extended from 28 days in light of a recent update issued by the European Centre for Disease Prevention and Control.

The HFEA also states that anyone who has been infected with the Zika virus should not donate gametes, conceive naturally or proceed with fertility treatment for six months. However, in light of evidence, the study researchers have said that guidelines may need to be reviewed, and that the finding may have implications also for screening measures at sperm banks.

Zika virus is primarily vector-borne by the Aedes mosquito. However several cases of sexual transmission have been reported since the 2015-2016 outbreak of the disease in central and southern America. The World Health Organization (WHO) declared the disease an international public health emergency due to the association of the infection with birth defect in up to 5000 babies born with microcephaly— a fetal abnormality that results in small head size and brain damage.

Christian Lindmeier, spokesperson and communication officer for the WHO, told BBC News that questions still remain on the transmission threshold of the Zika virus in semen after six months.

'The Zika outbreak is a constantly evolving situation and every new piece of evidence is looked into and evaluated as to whether or not guidelines will need to be revised,' Lindmeier added.