12 January 2012
Murray Valley encephalitis and other mosquito borne diseases: advice for travellers to Australia – update
On 29 December 2011, the New South Wales (NSW) Ministry of Health issued a warning to residents and visitors to NSW advising them to take extra care to protect themselves against Murray Valley encephalitis (MVE).
This mosquito borne virus has been detected in NSW sentinel chicken flocks in NSW (Leeton, Hay and Moama in the south of the state and in the Macquarie Marshes, located in the west of the state approximately 100km from the townships of Brewarrina, Walgett, Nyngan and Coonamble). Chickens do not usually show symptoms if infected with MVE. However, presence of the virus in sentinel flocks acts as a warning system for human infection .
Department of Health surveillance in Western Australia (WA) during December 2011 has indicated that Kunjin virus and MVE activity has been detected in the Kimberly and Wheatbelt regions. Above average rainfall in October and November 2011, resulting in increased mosquito populations, is thought to be the cause of this .
A total number of 15 cases of MVE were reported in Australia for 2011, the highest number of cases recorded in the past 10 years . Higher rates of other mosquito-borne diseases were reported in Australia throughout 2011, including Barmah Forest virus, Kunjin virus and Ross River virus. This is also thought to be related to heavy rainfall . The peak time for mosquito borne infections in Australia is during the summer and autumn months (December to May).
Advice for travellers:
These infections are rare in UK travellers. Ross River virus is occasionally reported in UK travellers who have returned from Australia  and MVE and Kunjin are exceptionally rare. However, the Health Protection Agency, Special Pathogens Reference Unit reported one case of Kunjin virus infection in a UK traveller who had returned from Australia in June 2011 .
All travellers to NSW and WA should be vigilant about mosquito bite avoidance and be aware of symptoms of MVE. Initial symptoms can include fever, dizziness, drowsiness, headache, nausea and a stiff neck. Anyone experiencing these initial symptoms must seek immediate medical attention .
All travellers to Australia should practise insect bite avoidance measures.
Advice for health professionals:
MVE and Kunjin virus are rare infections that can be associated with encephalitis (inflammation of the brain). Barmah Forest and Ross River virus infections are febrile illnesses associated with headache, rash, joint pains and sometimes arthritis.
Health professionals should be alert to the possibility of mosquito borne diseases in anyone presenting with a febrile illness who has recently returned from risk areas in Australia. The appropriate samples, along with a full clinical and travel history, should be sent to the HPA Special Pathogens Reference Unit.
1. Department of Health, New South Wales. Health Warning to Avoid Mosquitoes. 29 December 2011. [Accessed 12 January 2012]. Available at:
2. Government of Western Australia Department of Health. Widespread activity of mosquito –borne diseases in Western Australia. 9 December 2011. [Accessed 12 January 2012]. Available at: http://www.health.wa.gov.au/press/view_press.cfm?id=1093
3. Australian Government Department of Health and Ageing. Number of notifications of Murray Valley encephalitis virus infection, Australia in the period of 1991 to 2011 and year-to-date notifications for 2012. 9 January 2012. [Accessed 12 January 2012]. Available at: http://www9.health.gov.au/cda/Source/CDA-index.cfm?CFID=2363681&CFTOKEN=1ca27240b9aca4d6-C23EADB4-D60E-BDAF-8804CDFD46C
4. NaTHNaC Clinical Update: Increased risk of mosquito-borne disease: advice for travellers to Australia – updated.31 May 2011. [Accessed 12 January 2012]. Available at: http://www.nathnac.org/pro/clinical_updates/iba_australia2_
5. Health Protection Agency. Illness in England, Wales and Northern Ireland associated with Foreign travel – a baseline report to 2002. HPA London. 2004. [Accessed 12 January 2012]. Available at: http://www.hpa.org.uk/web/HPAweb&HPAwebStandard/HPA
6. Personal Communication. Joanne Lawrence, Travel and Migrant Health Section, Health Protection Agency. 11 January 2012.