Arboviral Diseases

RESPONSE PROTOCOL FOR NSW PUBLIC HEALTH UNITS

Public health priority
Urgent for JE, MVE and Kunjin.

High for alphaviruses acquired in a low/no risk area and dengue.

Routine for other cases.

PHU response time
Respond to confirmed cases within a day of notification for flaviviruses, or within three days for alphaviruses. Enter confirmed cases on NDD within one working day for flaviviruses, or within five working days for alphaviruses.

Case management
Determine possible exposures for all flaviviruses, and for alphaviruses acquired in a low/no risk area.

Contact management
Nil

Last updated: 06 September 2004

1. Reason for surveillance

To identify and control cases of disease caused by arboviruses

To monitor the epidemiology of arboviral diseases and so inform the development of better prevention and control strategies.

2. Case definitions

Ross River Virus
A confirmed case requires laboratory definitive evidence only.

Laboratory definitive evidence

Isolation of Ross River (RR) virus, or

Detection of RR virus by nucleic acid testing, or

IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre to RR virus, or

Detection of RR-specific IgM.

Barmah Forest Virus
A confirmed case requires laboratory definitive evidence only.

Laboratory definitive evidence

Isolation of Barmah Forest (BF) virus, OR

Detection of BF virus by nucleic acid testing, or

IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre to BF virus, or

Detection of BF-specific IgM.

Sindbis Virus
A confirmed case requires laboratory definitive evidence.

Laboratory definitive evidence

Isolation of Sindbis (SIN) virus; or

Detection of SIN by nucleic acid testing; or

IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre to SIN and where cross-reactions with other alphaviruses have been excluded by neutralisation or other specific serology, or

Detection of SIN-specific IgM in the absence of Ross River virus OR Barmah Forest virus IgM.

Dengue
A confirmed case requires:

Laboratory definitive evidence, and

Clinical evidence.

Laboratory definitive evidence

Isolation of dengue virus, or

Detection of dengue virus by nucleic acid testing, or

IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre to dengue virus, proven by neutralisation or another specific test, or

Detection of dengue virus-specific IgM in serum, except in North Queensland. In North Queensland, dengue virus-specific IgM in serum is acceptable evidence ONLY when this occurs during a proven outbreak.

Confirmation of laboratory result by a second arbovirus reference laboratory is required if the case occurs in previously unaffected areas of Australia. Currently, north Queensland is the only area with the potential for indigenous (epidemic) dengue virus in Australia.

Clinical Evidence
A clinically compatible illness (e.g. fever, headache, arthralgia, myalgia, rash, nausea, and vomiting, with a possible progression to dengue haemorrhagic fever, dengue shock syndrome or meningoencephalitis).

Japanese Encephalitis
A confirmed case requires:

Laboratory definitive evidence, and

Clinical evidence.

Laboratory definitive evidence

Isolation of Japanese encephalitis virus, or

Detection of Japanese encephalitis virus by nucleic acid testing, or

IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre of Japanese encephalitis virus-specific IgG proven by neutralisation or another specific test, with no history of recent Japanese encephalitis or yellow fever vaccination, or

Detection of Japanese encephalitis virus-specific IgM in cerebrospinal fluid, in the absence of IgM to Murray Valley encephalitis, Kunjin and dengue viruses, or

Detection of Japanese encephalitis virus-specific IgM in serum in the absence of IgM to Murray Valley encephalitis, Kunjin and dengue viruses, with no history of recent Japanese encephalitis or yellow fever vaccination.

Confirmation of laboratory result by a second arbovirus reference laboratory is required if the case appears to have been acquired in Australia.

Clinical evidence
A clinically compatible febrile illness of variable severity associated with neurological symptoms ranging from headache to meningitis or encephalitis. Symptoms may include headache, fever, meningeal signs, stupor, disorientation, coma, tremors, generalised paresis, hypertonia, and loss of coordination. The encephalitis cannot be distinguished clinically from other central nervous system infections.

Kunjin Virus
A confirmed case requires:

Laboratory definitive evidence, and

Clinical evidence.

Laboratory definitive evidence

Isolation of Kunjin virus, or

Detection of Kunjin virus by nucleic acid testing, or

IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre to Kunjin virus, or

Detection of Kunjin virus-specific IgM in cerebrospinal fluid, or

Detection of Kunjin virus-specific IgM in serum in the absence of IgM to Murray Valley encephalitis, Japanese encephalitis or dengue viruses. This is only accepted as laboratory evidence for encephalitic illnesses.

Confirmation of laboratory result by a second arbovirus reference laboratory is required if the case occurs in areas of Australia not known to have established enzootic/endemic activity or regular epidemic activity.

Clinical evidence
Non-encephalitic illness
Acute febrile illness with headache, myalgia and/or rash, OR

Encephalitic disease
Acute febrile meningoencephalitis characterised by one or more of the following:

Focal neurological disease or clearly impaired level of consciousness

An abnormal CT or MRI scan or EEG

Presence of pleocytosis in the CSF

Asymptomatic disease
Case detected as part of a serosurvey should not be notified.

Murray Valley Encephalitis
A confirmed case requires:

Laboratory definitive evidence, and

Clinical evidence.

Laboratory definitive evidence

Isolation of Murray Valley encephalitis virus, or

Detection of Murray Valley encephalitis virus by nucleic acid testing, or

IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre to Murray Valley encephalitis virus, or

Detection of Murray Valley encephalitis virus-specific IgM in cerebrospinal fluid in the absence of IgM to Kunjin, Japanese encephalitis or dengue viruses, or

Detection of Murray Valley encephalitis virus-specific IgM in serum in the absence of IgM to Kunjin, Japanese encephalitis or dengue viruses. This is only accepted as laboratory evidence for encephalitic illnesses.

Clinical evidence
Non-encephalitic disease:
Acute febrile illness with headache, myalgia and/or rash, or

Encephalitic disease:
Acute febrile meningoencephalitis characterised by one or more of the following:

Focal neurological disease or clearly impaired level of consciousness, or

An abnormal computerised tomograph or magnetic resonance image or electroencephalograph, or

Presence of pleocytosis in cerebrospinal fluid.

Asymptomatic disease:
Case detected as part of a serosurvey should not be notified.

Flavivirus Infection—unspecified
Note:

It is recognised that some cases of human infection cannot be attributed to a single flavivirus. This may either be because the serology shows specific antibody to more than one virus, specific antibody cannot be assigned based on the tests available in Australian reference laboratories, or a flavivirus is detected that cannot be identified

Confirmation by a second arbovirus reference laboratory is required if the case cannot be attributed to a known Flavivirus

Occasional human infections occur due to other known flaviviruses, such as Kokobera, Alfuy, Edge Hill and Stratford viruses.

A confirmed case requires:

Laboratory definitive evidence confirmation, and

Clinical evidence.

Laboratory definitive evidence

Isolation of a flavivirus that cannot be identified in Australian reference laboratories or which is identified as one of the flaviviruses not otherwise classified, or

Detection of a flavivirus, by nucleic acid testing, that cannot be identified in Australian reference laboratories or which is identified as one of the flaviviruses not otherwise classified, or

IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre of flavivirus specific IgG that cannot be identified or which is identified as being specific for one of the flaviviruses not otherwise classified. There must be no history of recent Japanese encephalitis or yellow fever vaccination, or

Detection of flavivirus IgM in cerebrospinal fluid, with reactivity to more than one flavivirus antigen (Murray Valley encephalitis, Kunjin, Japanese Encephalitis and/or dengue) or with reactivity only to one or more of the flaviviruses not otherwise classified, or

Detection of flavivirus IgM in the serum, with reactivity to more than one flavivirus antigen (Murray Valley encephalitis, Kunjin, Japanese Encephalitis and/or dengue) or with reactivity only to one or more of the flaviviruses not otherwise classified. This is only accepted as laboratory evidence for encephalitic illnesses. There must be no history of recent Japanese encephalitis or yellow fever vaccination.

Clinical evidence
Non-encephalitic illness
Acute febrile illness with headache, myalgia and/or rash, or

Encephalitic disease
Acute febrile meningoencephalitis characterised by one or more of the following:

Focal neurological disease or clearly impaired level of consciousness

An abnormal CT or MRI scan or EEG

Presence of pleocytosis in the CSF.

3. Notification criteria and procedure

Arboviral diseases are to be notified by laboratories on diagnosis (ideal reporting by telephone within 1 hour of diagnosis for flaviviruses other than dengue). By routine mail for other arboviruses. Only confirmed cases should be entered onto NDD.

4. The diseases

Infectious agents
A number of arboviruses (arthropod borne viruses), known to be pathogenic for humans, are classified below. The arboviruses most commonly identified or with the most serious public health consequences that have been reported in NSW include Ross River, Barmah Forest, Murray Valley Encephalitis, and Kunjin. Other reported viruses include Stratford, Alfuy and Edge Hill.

Alphaviruses
Ross River, Barmah Forest, and Sindbis.

Flaviviruses
Murray Valley Encephalitis, Kunjin, Dengue 1, 2, 3 and 4, Kokobera, Japanese Encephalitis, Stratford, Alfuy and Edge Hill.

Mode of transmission
Arboviruses are transmitted by the bite of an infected mosquito. There is no evidence of direct person-to-person spread. Transmission by aerosol to laboratory workers has been reported.

Timeline
The incubation periods are shown below.

Arbovirus	Incubation period (days)
Ross River	3 to 21, typically 7 to 9
Barmah Forest	not clear, probably 7 to 10
Dengue	3 to 14, typically 5 to 8
Murray Valley Encephalitis	5 to 26, typically 7 to 14
Kunjin	not known, thought to be 5 to 26
Japanese Encephalitis	5 to 15
Other arboviruses	not known, thought to be 3 to 11

Clinical manifestations
Ross River and Barmah Forest viruses
The severity of Ross River and Barmah Forest virus infections is 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.

Dengue
Manifestations commonly include fever, headache, myalgia, arthralgia, anorexia, rash and a tendency to minor haemorrhage. Recovery may be associated with prolonged fatigue and depression. Infection with one serotype does not provide protection against other serotypes. Re-infection
with another dengue serotype may lead to dengue haemorrhagic shock.

Local transmission of dengue has not been reported in NSW for decades; however it does occur in travellers returning from endemic areas from time to time, including some areas of North Queensland where Aedes aegypti mosquitos are present.

Murray Valley Encephalitis, Japanese Encephalitis and Kunjin
Symptoms of Murray Valley Encephalitis (MVE), Japanese Encephalitis (JE) and Kunjin virus infections are variable, but typically include sudden onset of fever, anorexia and headache. Vomiting, nausea, diarrhoea, muscle aches and dizziness may also occur. Neurological dysfunction may be experienced with photophobia, lethargy, irritability, drowsiness, neck stiffness, confusion, ataxia, aphasia, intention tremor, convulsions, coma and death. Although only a small proportion of infections result in clinical disease, a quarter of symptomatic cases of MVE and JE are fatal and a further 25 percent result in permanent complications. Encephalitis following infection with Kunjin is probably rare.

Cases with Japanese Encephalitis are invariably febrile and may be stuporous or comatose. Generalised seizures may occur, especially in children. The case fatality rate is high (about 25 percent) and neurological complications occur in about half of the cases.

No cases of Murray Valley Encephalitis have been diagnosed in NSW since 1974. Some sentinel chickens in western NSW seroconverted to MVE and Kunjin in 2001 and to MVE in 2004. Cases occur sporadically in remote Northern Territory and northern Western Australia. Japanese Encephalitis has never been present in NSW. The first Australian-acquired cases were detected in Torres Straits Islanders in 1995. Kunjin is occasionally reported in NSW.

5. Managing single notifications

Response times
Investigation

On same day of notification of a confirmed case of a flavivirus other than dengue begin follow-up investigation & notify the CDB of the case details

Within three working days of notification of a confirmed case of dengue, or an alphavirus acquired in a low/no risk area (including the Sydney metropolitan area) begin follow-up investigation.

Investigation of notifications other than the two situations outlined above is at the discretion of the PHU Director.

Data entry

Within one working day of notification enter on NDD confirmed flavivirus cases on NDD

Within five working days of notification enter on NDD confirmed alphavirus cases on NDD.

Response procedure
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 all flaviviruses, and for alphaviruses acquired in low/no risk areas, PHU staff should ensure that action has been taken to:

Confirm the onset date and symptoms of the illness

Confirm results of relevant pathology tests, or recommend the tests be done (for flaviviruses, and alphaviruses thought to be acquired in low risk areas, encourage the managing doctor to take convalescent sera to confirm the diagnosis)

Ensure confirmation by a second test if the case has been acquired in a previously unaffected area

Find out if the case or relevant care-giver has been told what the diagnosis is before interviewing them

Seek the doctor's permission to contact the case or relevant care-giver

Review case management

Identify likely source of infection.

Case management
Investigation and treatment
Supportive treatment only.

Education
The case or relevant care-giver should be informed about the nature of the infection and the mode of transmission.

Exposure investigation
The case should be asked to recall if, in the incubation period, he or she had:

Been bitten by mosquitoes, or

Visited regions where arboviruses are endemic, or

Participated in recreational or other activities involving exposure to bushland or other mosquito habitat (as in, for example, gardening, bushwalking and picnicing).

Isolation and restriction
None.

Environmental evaluation
Clusters of any arboviral 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.

Contact management
Identification of contacts
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.

Treatment
Passive immunisation
None

Active immunisation
A vaccine is available for Japanese Encephalitis but is only recommended for travellers spending ≥1 month in rural areas in countries where the disease is endemic or in some of the Torres Strait Islands.

Antibiotic prophylaxis
None

Education
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 on RRV, BFV and MVE and reducing exposure to mosquitos are available on the NSW Health web site.

6. Managing special situations

Flaviviruses
MVE cases should be reported to the CDB on the day of report. 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.

Case clustering
Where the case is part of an unusual cluster of an arboviral infection and where a discrete exposure can be identified, consider an epidemiological investigation and issuing an alert to local residents and visitors.