What is Zika?
Zika virus is a flavivirus and is closely related to Japanese encephalitis, West Nile, Dengue, and yellow fever viruses. Since its discovery in Uganda in 1948 Zika has continued to expand its geographic range, from Africa and Asia to Pacific Islands, then, further afield to South and Central America and Caribbean.

Transmission
Zika, like dengue and chikungunya viruses are transmitted by mosquitos mostly active during the daytime. Rare instances of sexual transmission have been reported. Pregnant women who become infected with Zika virus can transmit the disease to their unborn babies, with potentially serious consequences.

The mosquito species (Aedes sp) that can spread Zika virus are not normally found in New Zealand however they are found in many other countries around the world. A total of 89 countries  had documented evidence of locally transmitted mosquito-borne transmission of Zika virus, distributed across all regions.

Symptoms can include: 

• low-grade fever
• arthralgia (joint aches), notably of small joints of hands and feet, with possible swollen joints
• myalgia (muscle aches)
•  headache, retro-ocular headaches (behind the eyes)
• conjunctivitis (pink eye)
• cutaneous maculopapular rash 

Zika virus infection usually causes a mild disease (except for pregnant women).

However, as Zika infection may cause a rash that could be confused with diseases such as measles or dengue, these serious diseases do need to be ruled out.

Diagnosis of Zika will first and foremost be based on symptoms, travel history and exclusion of other diseases including measles, rubella, and dengue.

The incubation period is typically 3–12 days. There is no specific therapy for Zika virus infection and acute symptoms typically resolve within 4–7 days.

Use paracetamol for pain and fever if needed. Until dengue can be ruled out do not take aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, given the risk of bleeding.

Serious complications from Zika virus infection are uncommon.

However, based on research to date, there is scientific consensus that Zika virus is a cause of microcephaly and other severe foetal brain abnormalities as well as Guillain-Barré syndrome. It is especially important that pregnant women take all steps to minimise risk of mosquito bites in countries with zika virus.

Zika outbreak in Thailand
The Zika virus disease has increased to levels not seen since before the 2016 epidemic in Thailand, with more than 750 people infected and at least 13 babies born with birth defects in 2023.  In comparison, 190 cases were reported in 2022 and 63 in 2021.

The World Health Organization has also reported a significant increase globally in dengue fever, which is also transmitted primarily by Aedes sp. mosquitos.

Prevention advice for travellers
There is currently no vaccine or specific treatment available to prevent Zika virus infection or disease. The majority of Zika viruses cases are acquired via mosquito bites, although sexual transmission of Zika virus infection can occur. The overall risk of sexual transmission of Zika virus is considered to be low. Pregnant women who become infected with Zika virus can transmit the disease to their unborn babies, with potentially serious consequences. Prevention of Zika relies primarily on avoidance of mosquito bites.

If travelling to Thailand or zika-affected areas, women who are pregnant or plan to become pregnant should consult with their health care provider.  Individuals should take all precautions to avoid mosquito bites, including the following:  

• Wear long-sleeved shirts and long pants.
•  Use insect repellents containing DEET, picaridin, oil of lemon eucalyptus (OLE), or IR3535. Always use as directed.
•  Insect repellents containing DEET, picaridin, and IR3535 are safe for pregnant and breastfeeding women and children older than 2 months when used according to the product label. Oil of lemon eucalyptus products should not be used on children under 3 years of age.
•  If you use both sunscreen and insect repellent, apply the sunscreen first and then the repellent.
•  Use permethrin-treated clothing and gear (such as closed-toe shoes or boots, pants, socks, and tents).
•  Use bed nets, as necessary.
•  Stay and sleep in screened-in or air-conditioned rooms.
•  Be particularly vigilant for the 2 hours after sunrise and the 2 hours before sunset. 

Women who have travelled to an affected country without their partner should use appropriate contraception for eight weeks to avoid pregnancy. However, if the partner has also travelled to an affected country, then see advice on sexual transmission of Zika virus.

Note: Avoiding mosquito bites will help prevent infection with a number of viruses that can cause serious illness. In addition to Zika virus disease, mosquitos are the prime vector for infection with, and transmission of chikungunya, dengue, Japanese encephalitis, West Nile virus, and yellow fever.

More information about Zika virus can be found on the Te Whatu Ora or World Health Organisation websites.

Reviewed:14 May 2024, 11:40