How Zika got here could remain a mystery, say experts

How did the Zika virus trigger a recent outbreak in Singapore? Infectious diseases experts say this could be a mystery, as existing tests are unreliable for infections more than two weeks old.

“If a compatible mosquito bites someone who has the virus in his or her blood, the mosquito becomes infected. After about a week, the virus can be detected in the mosquito’s saliva, and the mosquito can then infect all the other people that it bites,” explains Associate Professor Hsu Li Yang on the process of transmission.

“If these other infected people are bitten by other mosquitoes during the days when the virus is circulating in their blood (which is usually three to 12 days after being bitten by an infected mosquito), the virus will be passed to these mosquitoes, and the cycle of infection will continue,” he added.

Transmission is also possible through sexual intercourse, though it is a less common means of infection. A/Prof Hsu explains that based on reported cases, the virus can remain in semen for more than six weeks.

For protective measures, infectious disease experts urge the public to protect themselves from mosquito bites by using repellent or wearing more clothing, and not travelling to Zika-infected countries. Pregnant women in their first trimester should also take extra precaution as the risk to the foetus is highest, A/Prof Hsu said.

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