The Zika virus is primarily transmitted to humans via the bite of an infective Aedes mosquito (Aedes aegypti and Aedes albopictus are the common species found locally).

The virus can also be passed from a pregnant woman to her foetus. Infection during pregnancy can cause certain birth defects, including microcephaly (baby’s head is much smaller than expected).

Sexual transmission has also been reported.

Incubation period: 3 to 14 days.

Infectious period: From 2 days before onset of illness and up to 3 months after onset.

Clinical features

Most people infected with the Zika virus do not develop symptoms. 1 in 5 cases may present with the following symptoms:

Rash
Fever
Conjunctivitis
Muscle pain
Joint pain
Headache

Symptoms usually appear within 3 to 14 days of being bitten by an infected Aedes mosquito. They tend to be mild and can last 4 to 7 days.

Risk factors

Living in or travelling to Zika-affected areas.

Although rare, serious neurological complications and foetal abnormalities have been associated with Zika virus infection. Currently there is no evidence that pregnant women are more likely to contract the Zika virus. However, the consequences can be more serious if a pregnant woman is infected, as Zika virus infection can cause microcephaly in a small number of unborn foetuses.

Diagnosis

RT-PCR test is able to detect Zika infection in blood within 5 to 7 days of onset of symptoms and in urine within 14 days of onset.

Zika serological tests should not be used for diagnosis of Zika virus infection due to cross-reactivity with dengue virus.

Treatment and management

There is no specific treatment or vaccine for Zika virus infection. The treatment is generally supportive.

If patient is not pregnant: Symptoms will be managed as they present themselves. There is no specific anti-viral medication to treat Zika virus infection.

If a male patient is planning a pregnancy with his partner or his partner is already pregnant: Patient should be advised to practise safe sex through correct and consistent use of condoms or abstain from sexual intercourse for at least 3 months after recovery.

If a female patient is planning a pregnancy: Patient should be advised to practise safer sex through the correct and consistent use of condoms or abstain from sexual intercourse for at least 2 months after recovery.

If the patient is pregnant: Patient should be referred to an O&G doctor so that their condition can be further managed.

Precaution, prevention, and control

Preventing the breeding of the Aedes mosquito remains the most effective way to control the spread of the Zika virus infection in Singapore.

Prevention measures include:

Staying in rooms which are well-screened or air-conditioned
Removing stagnant water in their environments
Wearing long, covered clothing
Applying insect repellent that contains DEET, Picaridin, or IR3535 as the active ingredient

During Pregnancy: For couples whose partner works, studies, or lives in an affected area, they should adopt safe sexual practices (e.g. consistent and correct use of condoms during sex) or consider abstinence throughout their pregnancy.

If a pregnant person’s partner has tested positive for Zika, they should consult their doctor and inform them of their possible exposure to Zika so that the doctor can arrange testing for them if necessary. The World Health Organization’s May 2016 guidelines do not recommend routine Zika testing for asymptomatic pregnant women. If the person is concerned, they should discuss further with their doctor.

For couples planning pregnancy

If the couple are well: They should take strict precautions against mosquito bites, and if they have further questions, consult their doctor.

If the woman is symptomatic: She should seek medical attention promptly, and if confirmed positive for Zika, she should practice safer sexual practices or abstain from sexual intercourse for at least 2 months after recovery, before trying to conceive.

If the man is symptomatic: He should seek medical attention promptly, and if confirmed positive for Zika, he should practice safer sex through the correct and consistent use of condoms or abstain from sexual intercourse for at least 3 months after recovery.

Notification

Who should notify:

Medical practitioners
Laboratories

When to notify:

On clinical suspicion or laboratory confirmation

How to notify:

Please refer to the Infectious Disease Notification for more information.

Notification timeline:

As soon as possible. No later than 24 hours from the time of diagnosis.

Resources

Please refer to the Weekly Infectious Diseases Bulletin for the number of confirmed Zika cases in Singapore.

You may also refer to the National Environment Agency website on Zika cases and clusters.