Increased Mosquito-borne Illness Risk In Australia

The Public Health Agency of Canada is currently monitoring increased activity of Ross River virus and Barmah Forrest virus in Australia.

During the month of January 838 cases of Ross River virus infections were reported nationally with Queensland and New South Wales reported the highest rates to date; Queensland (359), New South Wales (159). This is approximated 4 times the 5 year average rate.

There were a total of 127 cases of Barmah forest virus infection reported during January estimated to be 2 times the 5 year average rate.

Sources: Australian Department of Health and Aging, Department of Health, Government of Western Australia

Disease Information

Ross River (RRV) virus and Barmah Forest (BFV) virus are two important mosquito-borne viruses that cause human disease in Australia. The two viruses have similar life cycles and cause similar symptoms in people.

Ross River virus (RRV) disease is a viral infection spread by infected mosquitoes. Fewer than one in three humans will become infected after being bitten by an infected mosquito. Ross River virus infection cannot be passed from person to person. Symptoms of RRV disease vary from person to person, but commonly include painful and swollen joints, sore muscles, aching tendons, skin rash, fever, fatigue, headache and swollen lymph nodes. It generally results in a self-limiting flu-like illness, but it can cause long-term joint pain and fatigue. For more information on RRV, please visit the Travel Medicine Program's Disease Information Backgrounder on Ross River virus.

Barmah Forrest virus (BFV) disease, like RRV, is a viral infection spread by infected mosquitoes that cannot be passed from person to person. Symptoms of BFV disease vary from person to person, but commonly include painful and swollen joints, sore muscles, aching tendons, skin rash, fever, fatigue, headache and swollen lymph nodes. It generally results in a self-limiting flu-like illness, but it can cause long-term joint pain and fatigue. Rash tends to be more common to BFV disease and swollen joints are not as common and may not last as long as with RRV disease..Research suggests that BFV disease may last for a shorter period of time compared to RRV.

Recommendations

The Public Health Agency of Canada reminds travellers to Australia that they may be at risk for contracting mosquito-borne diseases, such as Ross River virus, Barmah Forrest virus, Murray Valley encephalitis, Kunjin virus as well as other less common mosquito-borne viruses. Travellers are strongly encouraged to consult their personal physician or a travel medicine practitioner to discuss their individual risk of exposure to such diseases.

Personal Measures to Avoid Mosquitoes

The Public Health Agency of Canada strongly recommends that travellers take the following personal precautions to reduce the risk of being bitten by day or nighttime feeding mosquitoes:

• remain in well-screened or completely enclosed, air-conditioned areas;
• wear light-coloured clothing with full-length pant legs and sleeves; and
• use insect repellent on exposed skin.

The use of insect repellent on exposed skin is strongly recommended. Of the insect repellents registered in Canada, those containing 'N, N diethyl-m-toluamide' (DEET) are the most effective. There are specific things you should know about DEET, especially regarding its use on young children.

• use DEET-based products as repellents on exposed skin. The higher the concentration of DEET in the repellent formulation, the longer the duration of protection. However, this relation reaches a plateau at about 30% to 35%. DEET formulations that are "extended duration" (ED), such as polymers, are generally considered to provide longer protection times, and may be associated with less DEET absorption. Formulations over 30% are not currently available in Canada, although they are available internationally, including in the United States. It should be noted, however, that products sold outside Canada have not been evaluated by Health Canada. Most repellents containing "natural" products are effective for shorter durations than DEET and for this reason are not considered the preferred products for protecting against mosquito bites.

• Regulatory agencies in western nations may differ regarding the recommended maximum concentration and application rates of DEET, especially for children. The Committee to Advise on Tropical Medicine and Travel (CATMAT) is satisfied that, for travel outside of Canada where the risk of malaria outweighs the risk of any important adverse reaction to DEET, the threshold for use of DEET should be low.

• CATMAT recommends that concentrations of DEET up to 35% can be used by any age group.

• For children, alternative personal protective measures, such as mosquito nets treated with insecticide, should be the first line of defense, especially for infants less than 6 months of age. Portable mosquito nets, including self-standing nets, placed over a car seat, a crib, playpen, or stroller help protect against mosquitoes. However, as a complement to the other methods of protection, the judicious use of DEET should be considered for children of any age. Recent medical literature from Canada suggests that DEET does not pose a significant or substantial extra risk to infants and children.

• DEET/sunscreen combination products are not generally recommended, because DEET can decrease the efficacy of sunscreens. As well, sunscreens should be used liberally and often while DEET should be used sparingly and only as often as required. If application of both is necessary, the Canadian Dermatology Association recommends that the sunscreen be applied first and allowed to penetrate the skin for 20 minutes, prior to applying DEET.

The Public Health Agency of Canada's Committee to Advise on Tropical Medicine and Travel (CATMAT) produces evidence based statements and guidelines. For additional information on Arthropod Bite Prevention visit CATMAT's Statement on Personal Protective Measures to Prevent Arthropod Bites.

As a reminder...

The Public Health Agency of Canada routinely recommends that Canadian international travellers consult their personal physician or a travel clinic four to six weeks prior to international travel, regardless of destination, for an individual risk assessment to determine their individual health risks and their need for vaccination, preventative medication, and personal protective measures.

The Public Health Agency of Canada recommends, as well, that travellers who become sick or feel unwell on their return to Canada should seek a medical assessment with their personal physician. Travellers should inform their physician, without being asked, that they have been travelling or living outside of Canada, and where they have been.

Additional Information

For comprehensive information on Ross River virus.

For comprehensive information on Barmah Forrest virus.

For more information about Ross River virus infection in Western Australia, visit the Department of Health, Government of Western Australia.

For current and past case numbers in Australia, consult Communicable Diseases Australia(CDA) - National Notifiable Diseases Surveillance System(NNDSS)