Zika virus disease – Viet Nam

• The first case, a resident of Nha Trang, Viet Nam, had onset of fever, rash, conjunctivitis and headache on 26 March 2016. On 31 March, the case tested positive for Zika virus infection by polymerase chain reaction (PCR) at Pasteur Institute Nha Trang. On 4 April the result was confirmed by the Pasteur Institute Ho Chi Minh City and National Institute of Hygiene and Epidemiology.
• The second case, a resident of Ho Chi Minh City, Viet Nam, developed rash, conjunctivitis and malaise on 29 March 2016. On 31 March the case tested positive for Zika virus infection by PCR at Pasteur Institute Ho Chi Minh City. On 2 April the result was confirmed by the National Institute of Hygiene and Epidemiology, and again on 4 April by the Nagasaki University.

As of 4 April, the National Institute of Hygiene and Epidemiology and Pasteur Institutes of Ho Chi Minh City and Nha Trang have tested 1,215 samples collected from people with Zika virus symptoms from 32 provinces in Viet Nam. No other cases of Zika virus infection have yet been identified.

Health authorities in Viet Nam are taking the following measures:

• strengthening disease surveillance and vector control activities;
• implementing risk communication activities, and provide information on measures for prevention and control of Zika virus and other mosquito borne diseases;
• implementing measures for monitoring the health status of pregnant women and detecting possible foetal complications of Zika virus infection;
• supporting medical facilities, including obstetric and paediatric units to prepare for a potential increase in the demand of health care services;
• ensuring adequate resource allocation for Zika prevention and control activities.

These are the first autochthonous cases of Zika virus infection detected in Viet Nam in 2016. This report does not change the overall risk assessment. The risk of a global spread of Zika virus to areas where the competent vectors, the Aedes mosquitoes, are present is significant given the wide geographical distribution of these mosquitoes in various regions of the world. WHO continues to monitor the epidemiological situation and conducts risk assessment based on the latest available information.

The proximity of mosquito vector breeding sites to human habitation is a significant risk factor for Zika virus infection. Prevention and control relies on reducing the breeding of mosquitoes through source reduction (removal and modification of breeding sites) and reducing contact between mosquitoes and people. This can be achieved by reducing the number of natural and artificial water-filled habitats that support mosquito larvae, reducing the adult mosquito populations around at-risk communities and by using barriers such as insect screens, closed doors and windows, long clothing and repellents. Since the Aedes mosquitoes (the primary vector for transmission) are day-biting mosquitoes, it is recommended that those who sleep during the daytime, particularly young children, the sick or elderly, should rest under mosquito nets (bed nets), treated with or without insecticide to provide protection. Mosquito coils or other insecticide vaporizers may also reduce the likelihood of being bitten.

During outbreaks, space spraying of insecticides may be carried out following the technical orientation provided by WHO to kill flying mosquitoes. Suitable insecticides (recommended by the WHO Pesticide Evaluation Scheme) may also be used as larvicides to treat relatively large water containers, when this is technically indicated.

Basic precautions for protection from mosquito bites should be taken by people traveling to high risk areas, especially pregnant women. These include use of repellents, wearing light colored, long sleeved shirts and pants and ensuring rooms are fitted with screens to prevent mosquitoes from entering.

Although the risk of transmission of Zika virus through sexual activity is considered to be very limited, based on precautionary principles, WHO recommends the following:

• All patients (male and female) with Zika virus infection and their sexual partners (particularly pregnant women) should receive information about the potential risks of sexual transmission of Zika virus, contraceptive measures and safer sexual practices, and should be provided with condoms when feasible. Women who have had unprotected sex and do not wish to become pregnant because of concern with infection with Zika virus should also have ready access to emergency contraceptive services and counselling.
• Sexual partners of pregnant women, living in or returning from areas where local transmission of Zika virus is known to occur, should use safer sexual practices or abstinence from sexual activity for the duration of the pregnancy.
• As most Zika virus infections are asymptomatic:
• Men and women living in areas where local transmission of Zika virus is known to occur should consider adopting safer sexual practices or abstaining from sexual activity.
• Men and women returning from areas where local transmission of Zika virus is known to occur should adopt safer sexual practices or consider abstinence for at least four weeks after return.

Independently of considerations regarding Zika virus, WHO always recommends the use of safer sexual practices, including the correct and consistent use of condoms to prevent HIV, other sexually transmitted infections and unwanted pregnancies.

WHO does not recommend routine semen testing to detect Zika virus.

WHO does not recommend any travel or trade restriction to Viet Nam based on the current information available.