Study shows Zika virus more resilient than previously known

Although Zika virus only survives for a few days in the blood of infected persons, the virus can persist in the semen of male patients, causing testis injuries and infertility, new research suggests.

Scientists from China Agricultural University and the Institute of Microbiology, affiliated with the Chinese Academy of Sciences, conducted a study on the damage that Zika can cause to the male reproductive system.

They found that the virus can lead to inflammation of the testis and epididymis - a tube that carries and stores sperm - of infected male mice.

There was noticeable tissue atrophy on the eighth day of infection, massive die-off of sperm cells on the 16th day, destruction of tubes inside the testis within one month and complete shrinkage of the testis within two months.

The scientific journal Cell reported this research on Nov 22.

"The Zika virus is one pathogen in which we do not have a thorough understanding of the danger it can pose. It was discovered in 1947, but did not attract much attention until the latest outbreak in Brazil during 2015, mainly due to worries about the association of virus infection with brain damage in babies," said Gao Fu, an academician and professor at the Institute of Microbiology and deputy director of China CDC, who is a corresponding author of this study.

"China is a country with a large population, and the government just adopted the universal second-child policy. As a result, the challenge that Zika virus poses to China is much more severe than that from other viruses, like Ebola and bird flu," he said.

Moreover, the study finds that while Zika virus infects the testis and epididymis, it does not spread to the prostate or seminal vesicle, which is another part of the male reproductive system.

"This discovery may suggest that only certain types of cells are vulnerable to virus infection, and these cells may be the potential repositories for Zika virus," said Li Xiangdong, a professor with the China Agricultural University and a corresponding author of the research.

"The persistence of Zika virus in cells is a warning of the potential risks the virus poses to male reproductive health. Sperm banks may need to be re-inspected for Zika virus infections to ensure safety of their products," she said.

In February, the Centers for Disease Control and Prevention in the US confirmed a case of sexually-transmitted Zika virus infection.

"This is the starting point of our research. As the virus disappears quickly from the blood of infected persons, they must persist somewhere else in the person, so that it could be transmitted by sexual activity," said Gao.

Earlier this month, a study conducted by a team from Washington University and was published in Nature had reported similar conclusions.

However, the Chinese team's study was more comprehensive.

"First, we studied the entire reproductive system, but the study from Washington University focused mainly on the testis and epididymis. Second, we used a humanized antibody to track the exact location of Zika virus in the cell, which provides a better clue for further studies into the pathogenic mechanism(s) of the virus," he said.

By Nov 10, 72 countries and regions had reported cases of the Zika virus infection in humans.