West Nile Virus (WNV)

What is West Nile virus?

West Nile virus is an infection that can cause a mild ‘flu-like illness that typically lasts between three and six days. Most people who become infected by West Nile virus have no symptoms. West Nile virus is mainly spread through the bite of an infected mosquito. 

What are the symptoms of West Nile virus?

About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhoea or rash. Most people with this type of West Nile virus disease recover completely, but tiredness and weakness can last for weeks or months. The time between being infected with West Nile virus and developing symptoms is usually between 3 and 14 days. People over 50 year of age and those with weakened immune systems e.g. people living with cancer, may have more severe symptoms, but full recovery is usually the rule. 

How is West Nile virus spread?

West Nile virus is spread when a person is bitten by an infected mosquito. Other less common possible forms of transmission include:

  • from a blood transfusion, organ transplant or breast milk

  • contact with other infected animals, their blood or other tissues 

There is one reported case of mother to baby transmission during pregnancy to date. While transmission of WNV to laboratory workers has been reported, no transmission of WNV to health care workers has been reported when standard infection control precautions have been put in place. 

West Nile virus is not spread by the following:

  • regular social contact

  • sexual contact

  • usage of communal household utensils

  • caring for someone with West Nile virus 

Can West Nile virus be spread through blood?

West Nile virus can be transmitted through blood. People who have travelled to affected areas should not give blood (www.giveblood.ie). 

How is West Nile virus treated?

There is no vaccine or specific drug for West Nile virus. However, treatment consists of relieving pain, fever and any other symptom that inconveniences the patient. To prevent dehydration, patients should control the fever, rest and drink plenty of water. 

How is West Nile virus diagnosed?

Laboratory tests are currently available for blood and cerebrospinal fluid (CSF) from patients with symptoms. 

Have cases of West Nile virus been diagnosed in Ireland?

West Nile virus infection has been diagnosed in a small number of travellers returning from affected areas. All have recovered fully. 

Are people in Ireland at risk of West Nile virus?

West Nile virus can be imported into Ireland in a traveller returning from an affected area. 

What countries are affected by West Nile virus?

West Nile virus is commonly found in Africa, Europe, the Middle East, North America and West Asia. 

What is the current travel advice?

The Department of Foreign Affairs and Trade (DFA) provides guidance to travellers that is updated regularly. Please consult the DFA website and click on the relevant country. It is important to check this information prior to any trips, as the situation could change rapidly. 

What do I do if I’m living / working in an area where West Nile virus is circulating?

If you become ill you should contact your local health care provider who will be able to advise on your individual circumstances. 

What do I do if I am travelling to an area where West Nile virus is circulating?

  • All travellers going to an area affected by West Nile virus should take measures to prevent transmission.

  • Irish citizens who live in affected areas should also take measures to prevent transmission.

  • People showing symptoms suggestive of West Nile virus infection within three days after returning from an affected area should contact their healthcare provider.

Please see further travel advice on the HPSC website. 

What do I do if I’m returning to Ireland from an area where West Nile virus is circulating?

If you become ill upon your return to Ireland, you should contact your doctor for assessment and let him/her know of your recent travel history to an affected area. 

Updated: 16th January 2019