Public health priority: High for cases acquired in a low/no risk area. Routine for other cases.
PHU response time: Respond to confirmed cases within three days. Enter confirmed and probable cases on NCIMS within five working days.
Case management: Determine possible exposures for cases acquired in a low/no risk area.
Contact management: Nil
Both confirmed cases and probable cases should be notified.
A confirmed case requires laboratory definitive evidence only.
A probable case requires laboratory suggestive evidence only.
Ross River virus cases are to be notified by laboratories on diagnosis by routine mail. Probable and confirmed cases should be entered onto NCIMS.
Ross River virus is one of the arboviruses (arthropod borne viruses) known to be pathogenic for humans. The Ross River virus is a member of the genus Alphavirus, in the family Togaviridae (Barmah Forest virus, Sindbis and chikungunya are also alphaviruses).
The Ross River virus is transmitted by the bite of an infected mosquito. There is no evidence of direct person-to-person spread. Humans are infectious to mosquitoes for the first few days after the onset of illness. Infected individuals can introduce the virus into receptive areas.
The incubation period can range from 3 to 21 days but is typically 7 to 9 days.
The severity of Ross River infections are variable and most are asymptomatic. Typical symptoms include rash (particularly on palms), polyarthritis/arthralgia, myalgia, lethargy and low-grade fever. Symptoms such as arthralgia, myalgia and lethargy may occasionally persist for many months.
Ross River and Barmah Forest infections are by far the most commonly observed arboviruses in NSW.
Within three working days of notification of a Ross River case acquired in a low/no risk area (including the Sydney metropolitan area) begin follow-up investigation.
Investigation of notifications outside of this is at the discretion of the PHU Director.
Within five working days of notification enter probable and confirmed cases on NCIMS.
The response to a notification will normally be carried out in collaboration with the case's health carers. But regardless of who does the follow-up for Ross River cases acquired in low/no risk areas, PHU staff should ensure that action has been taken to:
Supportive treatment only.
The case or relevant care-giver should be informed about the nature of the infection and the mode of transmission.
The case should be asked to recall if, in the incubation period, he or she had:
Clusters of Ross River disease occurring in an atypical geographical area may indicate the need for extraordinary mosquito investigation and control measures and other environmental management strategies and/or health information for the community. This should be discussed with NSW Health Department's Centre for Health Protection.
Potentially exposed people are those who may have been exposed to the same source as the case. However, active searching for these people is not usually indicated.
Educate the public living in or travelling to endemic areas to minimise exposure to mosquito bites. Information should indicate geographical location of habitats, and periods of maximum mosquito activity and also refer to protective clothing, appropriate repellents and methods of reducing mosquitoes in the home. Fact sheets are available.
Where the case is part of an unusual cluster and where a discrete exposure can be identified, consider an epidemiological investigation and issuing an alert to local residents and visitors.