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Zika Virus Disease

by Dr Bob Kass - January 25, 2016

Zika Virus Infection

UPDATE January 25, 2016: Centers for Disease Control and Prevention has posted Level 2 Alert travel notices (Practice Enhanced Precautions) for Zika in a number of countries following reports of birth defects in babies of mothers who were infected with Zika virus while pregnant. 

There has been a good deal of media attention on Zika virus infection in the last few weeks. 

Studies are now underway to investigate the validity of a possible link between Zika virus infection during pregnancy and infants born with microcephaly (small head circumference). Reports of microcephaly have increased on average 20 fold in a number of states located in NE Brazil. This region experienced a major outbreak of Zika virus infection in 2015. The increase in microcephaly was not reported across all states.

A number of other regions (Africa, SE Asia and French Polynesia) have also experienced outbreaks of Zika virus infection and this link needs to be investigated in these regions as well.  It is currently not known whether the relationship is causal (definite link) or casual (happening at the same but due to some other factor).  We will know more about this in coming months.

Zika virus


Zika virus disease is usually mild, lasting 2 to 7 days. It is suggested that only 25% cases will have symptoms. Many cases go undiagnosed or misdiagnosed as dengue fever of chikungunya. The main clinical features are fever, conjunctivitis and pain affecting the small joints of the hands and feet. Occasionally there is a rash that starts on the face and then spreads to the rest of the body. Monkeys and humans are the likely vertebrate hosts.

Transmission is possible through blood transfusions, the placenta and breast feeding.  The virus has been identified in semen more than 2 weeks after recovery.


No vaccine or specific antiviral treatment  for Zika fever is available. Treatment is symptomatic: rest and extra fluids. Paracetamol may relieve symptoms of fever and aching. Aspirin and ibuprofen should be avoided as with dengue.

ZIKA timeline

Zika infection is not a new disease. 

   1947        Isolated for the first time from a rhesus monkey in Zika forest, Uganda.
The monkey was part of a research program investigating yellow fever.
Further studies showed humans could be infected.
 1968   Isolated from humans in Nigeria.
 1971-75   Infection rates of 40% identified in a region of Nigeria.
 > 1975  

Africa: Tanzania, Egypt, Central African Republic, Sierre Leone, Gabon

Asia: India, Malaysia, Philippines, Thailand, Vietnam, Indonesia
2007  Oceania: Yap Island
 Oct 2013  Oceania: French Polynesia (perhaps > 32,000 cases), New Caledonia, Cook Island,
Easter Island.

NE Brazil (“dengue-like-syndrome” identified as Zika)

Possible connection with the World Sprint Championship Canoe
race in August 2014 with contestants travelling from the Pacific to Brazil for the event. 
There was also a large influx of tourists for the 2014 FIFA World Cup. 
More than 1.3 million cases now suspected in Brazil.

Oceania: Samoa, Solomon Islands, New Caledonia, Fiji, Vanuatu

Other:  Colombia, Guatemala, El Salvador, Mexico, Panama, Venezuela


Travellers should:

  • be aware of the current  outbreak of Zika virus disease in South and Central America and the possibility of exposure in other regions.

  • use evidence-based personal preventive measures to reduce mosquito bites (see below)

  • seek expert advice on the risk of the disease and mosquito avoidance measures if they have risk factors which may result in serious disease ( immune deficiency, taking immune suppressive medication, pregnant or intending to become pregnant)

  • mention to their medical attendant if they have travelled to a risk area while pregnant.

Mosquito avoidance measures

Many  diseases can be spread by insects. These include malaria, dengue fever, japanese  encephalitis, yellow Fever, chikungunya and zika  to mention just a few.

 Insect-borne diseases pose a serious threat to travellers and it is important to reduce the number of insect bites as much as possible.  The fewer bites the better. 

The "mosquito magnet" needs to take special care as he/she might receive 10 bites  to the non "magnet's"  1.  Most individuals know quite early in life if they are a magnet. Possibly 1 in 3 of the population are in this category.  


  • Reduce exposure time by modifying activities. The malaria mosquito is most active between dusk and dawn with peak activity around 9pm. The "zika mosquito" prefers late afternoon and early morning.  It is very much a city mosquito.

  • Wear light-coloured clothing. Cover arms and legs as much as possible.

  • Tucking trousers into socks and not wearing sandals in areas with ticks.

  • Permethrin impregnation of clothing, camping gear and curtains.

  • Avoid highly-scented perfumes or toiletries.

  • Sleep in air-conditioned accommodation or under mosquito nets (preferably impregnated with permethrin)

  • Use personal repellents on exposed skin (see table).

  • Use insecticide aerosols, mosquito coils or other agents in the immediate environment


The repellents of choice should contain either DEET (20-30%)(N,N-diethyl-meta-toluamide) or Picaridin (20%) (KBR3023 or 1 methyl propyl 2-(2hydroxyethyl)-1piperidine carboxylate). These generally protect for 4-6 hours. The only “natural” product with evidence of protection is oil of lemon eucalyptus (p-methane 3,8-diol or PMD) which only protects for 2 hours. The higher the concentration the longer the product protects. Some people prefer the smell and feel of Picaridin and it is not as damaging to plastics if it leaks. DEET is toxic when ingested and may cause skin irritation in some people. DEET has been used over a long period of time and by many millions of people with few reported serious side effects. Despite this, a few precautions should be undertaken.

  • Apply DEET/ Picaridin lightly to exposed areas only

  • Where possible, wash off on returning indoors

  • Do not apply to open cuts or sores

  • Do not use aerosol applications to the face directly. Apply to the hands and then rub on the face avoiding eyes and mouth

  • Do not allow young children (under 10 years) to apply it to themselves. Special weaker formulations are available for children. If they have never used it before, it is wise to test a patch on the arm for a few days before applying all over.

  • If sunscreens are to be used with repellents then the sunscreen should be applied first.  Wait 20 minutes before using the repellent.

View Globe Medical's selection of DEET repellents from the Travel Shop

DEET concentration Protection Time
30% 8hrs
15% 5hrs
10% 3hrs
5% 2hrs



Permethrin is similar to a naturally occurring chemical called pyrethrum. Pyrethrum was initially derived from the flowers of the daisy Chrysanthemum. The insecticide properties of the flower have been recognized since the 18th century. The synthesized product has been available for over 30 years. It is colourless, odourless and biodegradeable.

Permethrin acts as a “knockdown” insecticide. It is not a repellent. It damages the central nervous system of insects which come into contact with it.

It is effective against many insects including mosquitoes, fleas, ticks, bedbugs, chiggers, scabies and flies. Permethrin-treated bednets have been found to significantly reduce malaria rates in children in Africa and the Western Pacific region.

Once opened to the air, the net should be treated every 6 months to retain its potency. Permethrin can also be used to impregnate clothes, tents and window drapes. It adheres well to fabrics like cotton and will remain effective for between 5 and 10 washes. It is not recommended for skin application.

Frequently Asked Zika Questions

Read our follow up Zika FAQ which includes 10 more facts to help you better understand the Zika virus.

The Travel Shop @ Globe Medical

Purchase recommended travel products including DEET repellents and permethrin treated bednets at Globe Medical's Travel Shop.

Image by © James Cathany 2007 CDC - National Center for Infectious Diseases


Dr Bob Kass

Dr Bob Kass is Medical Director of Globe Medical. He holds specialist qualifications in paediatrics and public health medicine and is one of Australia's pioneers in the discipline of Travel Medicine. 

Full professional biography