askST: Does getting Zika infection once confer immunity?

It should, but docs don't know enough to advise couples to get infected before starting a family

With the recent spike in Zika cases in Singapore, many readers wrote in with questions, ranging from whether they should get tested for the virus to the impact on expectant mothers.

Senior Health Correspondent Salma Khalik addresses their concerns.

Q What is Zika?

A It is a viral infection transmitted by the bite of an infected Aedes mosquito, which is also the carrier of dengue and chikungunya viruses.

Q What are the symptoms?

A It is generally a mild disease, with four in five people infected having no symptoms at all.

Those who get sick would usually have a mild fever, red itchy rash and also joint and muscle pain, headache, red eyes and may suffer from nausea and vomiting. These usually last from three to five days.

But it could be dangerous for unborn babies.

Q What is the danger to unborn babies?

A Reports from other countries say between 1 per cent and 13 per cent of pregnant women infected in the early half of their pregnancy risk having babies with microcephaly and other birth abnormalities.

Q What is microcephaly?

A Microcephaly is a birth defect where the baby has an unusually small head. It is not the size of the head that is the worry. It is the problems it causes: a poorly developed brain that can result in mental and physical retardation so the child has difficulty talking, walking, and even feeding properly. He also risks having hearing and vision impairment.

Q Can the pregnant mother be treated to prevent microcephaly once it is known that she has Zika?

A Not at the moment. The only thing doctors can do is to monitor the growth of the foetus. If screening shows abnormalities, the doctor will discuss the findings with the parents. If the pregnancy is less than 24 weeks, abortion is an option. If it is longer than that, the child has to be carried to term.

Q Why can't abortion be done if the pregnancy is more than 24 weeks?

A A baby that is older than 24 weeks can survive, but one that is less than 24 weeks cannot survive without medical support. If the baby survives, it would be disadvantaged by the short gestation. However, microcephaly is not always severe. Reports say 15 per cent of babies with microcephaly grow up normal.

Q Is the baby at risk throughout the pregnancy?

A Professor Arijit Biswas, clinical director of obstetrics and gynaecology at the National University Hospital, said the risk is highest during the first trimester and the early part of the second trimester of pregnancy. Though the risk is lower in the third trimester, the virus could still cause fatal outcomes such as stillbirth.

Q If a woman who is not pregnant is bitten by a mosquito and infected with the Zika virus, will her future pregnancies be at risk?

A The infection does not pose a risk of birth defects for future pregnancies, if it is more than two months after the woman has recovered from Zika.

Q Does getting infected once confer immunity?

A One infection should confer lifetime immunity against the disease, said Professor Leo Yee Sin, a senior infectious diseases consultant at the Communicable Disease Centre.

Q Should young couples try to get infected so they do not get the disease when they want to raise a family?

A Prof Leo said while this may sound logical, not enough is known about the disease to advise this course of action.

Q Should all pregnant women check to see if they have been infected with Zika, even if they have no symptoms?

A No, because the tests work only if they are carried out within a month of infection.

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A version of this article appeared in the print edition of The Straits Times on September 03, 2016, with the headline 'Does getting Zika infection once confer immunity?'. Subscribe