Chikungunya virus disease

Notification requirement for chikungunya virus disease

Chikungunya virus infection is a ‘routine’ notifiable condition and must be notified by medical practitioners and pathology services in writing within 5 days of diagnosis.

This is a Victorian statutory requirement.

Primary school and children’s services centre exclusion for chikungunya virus disease

Exclusion is not applicable.

Infectious agent of chikungunya virus disease

Chikungunya is an alphavirus of the family Togaviridae and is related to Ross River virus, Barmah Forest virus and Sindbis virus.

Identification of chikungunya virus disease

Clinical features

Chikungunya virus infection causes illness characterised by an abrupt onset of fever, headache, rash and severe joint pain in approximately 70 per cent of cases. The acute disease lasts 3–10 days, but convalescence may include prolonged joint swelling and pain lasting weeks or months.

Diagnosis

Diagnosis may be determined with the following tests:

• isolation of chikungunya virus
• detection of chikungunya virus by nucleic acid testing
• seroconversion or a significant rise in antibody level or a fourfold or greater rise in titre to chikungunya virus, in the absence of a corresponding change in antibody levels to Ross River virus and Barmah Forest virus
• detection of chikungunya virus–specific IgM, in the absence of IgM to Ross River virus and Barmah Forest virus.

Early diagnosis (within 5 days of illness onset) can be readily done through polymerase chain reaction (PCR) testing, and later (5 days or more after illness onset) through IgM detection.

Incubation period of chikungunya virus

Onset of illness usually occurs between 4 and 8 days after the bite of an infected mosquito, but can range from 2 to 12 days. Asymptomatic infections can occur, but the incidence of this is unknown.

Public health significance and occurrence of chikungunya virus disease

The disease occurs in Africa, the Arabian Peninsula, South and South-East Asia. Human infections in Africa have been at relatively low levels for a number of years, but in 1999–2000 a large outbreak occurred in the Democratic Republic of the Congo, and in 2007 there was an outbreak in Gabon. In recent decades, mosquito vectors of chikungunya have spread to Europe and the Americas. Disease transmission was reported for the first time in Europe in 2007, in a localised outbreak in north-eastern Italy, and in the Americas (St Martin and Martinique in the Caribbean) in 2013. Chikungunya has also been spreading eastwards through Indonesia since 2002 and was detected in Papua New Guinea in 2012.

No locally acquired cases have been reported in Australia, and there is no evidence confirming incursions of chikungunya into Australia. However, a few visitors and returning residents entering Australia have been diagnosed with the disease. There is the potential for significant socioeconomic impact should it become established in Australia.

Reservoir of chikungunya virus

Humans and monkeys are the main hosts of chikungunya, but the range of vertebrate hosts is not well understood. The possibility of Australian animal species acting as hosts has not been determined; recently, bats have been indicated as a possible host.

Mode of transmission of chikungunya virus

The virus is transmitted from human to human by the bites of infected female mosquitoes. The mosquitoes usually involved are Aedes aegypti and A. albopictus, two species that can also transmit other mosquito-borne viruses, including dengue. Other mosquitoes such as Mansonia spp. may also be involved.

These mosquitoes are active throughout daylight hours, although there may be peaks of activity in the early morning and late afternoon. Both species are found biting outdoors, but A. aegypti will also readily feed indoors.

Period of communicability of chikungunya virus

There is no evidence of direct person-to-person transmission.

Susceptibility and resistance to chikungunya virus disease

Once a person has recovered from chikungunya disease, they are unlikely to get it again.

Control measures for chikungunya virus disease

Preventive measures

The best way to avoid chikungunya virus infection is to prevent mosquito bites, particularly during the day. Travellers should take the following precautions to reduce their risk of chikungunya infection:

• avoid mosquito-prone areas
• ensure accommodation is mosquito-proof. Use mosquito nets, flying insect spray, mosquito coils or plug-in insecticide mats in rooms
• use personal repellents containing diethyltoluamide (DEET) or picaridin
• wear long, loose-fitting, light-coloured protective clothing.

No vaccine or preventive drug provides protection against Chikungunya infection.

Control of case

Second attacks are unknown. Treatment is symptomatic; rest is advisable in the acute stages of the disease.

Control of contacts

Contact tracing for chikungunya is not generally applicable; however, if a case is suspected of contracting the illness in Australia, unreported or undiagnosed cases should be sought in the region where the case was staying during the incubation period of their illness.

Control of environment

Since chikungunya has not yet been acquired in Australia (people have only acquired their illness overseas), environmental evaluation is not routinely necessary.

Outbreak measures for chikungunya virus disease

In the event of a locally acquired outbreak, the following measures may be considered:

• Airport vector control may be necessary to prevent spread from endemic areas to other countries where local vectors such as A. aegypti can transmit the disease.
• Where a flavivirus appears to have occurred through exposure to a mosquito vector in the local area, enhanced surveillance through active case finding is recommended.
• Conduct a survey of mosquitoes to determine the species of vector mosquito involved (through virus detection and isolation)
• Identify vector breeding places and promote their control.
• Promote the use of mosquito repellents and other mosquito avoidance measures for people exposed to bites because of their occupation, or other reasons.
• Implement travel restrictions to the outbreak area.
• Avoid contact with the vector.