According to a new study, shrunken testicles may soon be added to the list of possible side effects of the Zika virus. Researchers from Yale University found that Zika infections reduced the size of mice testes. The team is now investigating whether this shrinking also occurs in humans, and if so, whether it will affect male fertility.

The study, now published online in Science Advances, found that 21 days after Zika infection, the testes of infected mice were significantly smaller than those of control mice. This condition, known as testicular atrophy, is often a sign of compromised male fertility. In addition, the Zika virus continued to replicate in the testicular cells even after it had cleared from the blood.

“This study shows how the Zika virus replicates in and damages testes," said first author Ryuta Uraki in a statement. "These results suggest that infection can cause reproductive deficiency in males."

Read: Zika Sexual Transmission And Pregnancy Risks Update

For their research, the scientists exposed mice to a non-lethal form of the Zika virus in order to observe how it behaved inside the body. The mice had been genetically altered to make this observation easier. The team observed that the virus stayed in a storage compartment of the male reproductive system known as the epididymis. This area connects sperm in the testicles to the urethra, and may explain how the virus is spread from males to females via sexual activity.

Mosquito bites are the main vector of transmission for Zika virus. The fact that Zika can spread through sexual activity is new information and was only identified last year. Although the Zika virus has existed for centuries, it was only in the recent outbreak that occurred in Brazil last year that scientists noted the disease also caused some pregnant women to give birth to children born with microcephaly, a serious birth defect that caused brain underdevelopment.

At the moment, it’s not clear whether Zika virus causes fertility problems in infected men, although the team admitted that results would suggest this. For example, testicular atrophy is often associated with low sperm production, low testosterone, and reduced libido, Info Varicocele reported.

The researchers report that these findings further highlight the need to develop an effective vaccine against the Zika virus, although the World Health Organization recently explained that this is not likely to happen before the year 2020.

Source: Uraki R, Hwang J, Jurado KA, et al. Zika virus causes testicular atrophy. Science Advances . 2017

See Also:

Is There A Cure For Zika? Everything You Need To Know About The Mosquito-Borne Disease

Zika Early Symptoms 2016: Warning Signs That You're Infected And What To Do