Page content: Victorian statutory requirement | Infectious agent | Identification | Incubation period | Public health significance & occurrence | Reservoir | Mode of transmission | Period of communicability | Susceptibility & resistance | Control measures | Outbreak measures | International measures | Additional sources of information

Victorian statutory requirement

Viral haemorrhagic fever (Group A disease) must be notified immediately by telephone or fax followed by written notification within five days.

School exclusion: until medical clearance.

Crimean-Congo, Ebola, Lassa and Marburg viral haemorrhagic fevers are subject to Australian quarantine.

Infectious agent

Four viral haemorrhagic fevers (VHFs) are of particular concern because they could be imported into Australia and be transmitted to other people, particularly health care personnel by blood or body fluid inoculation. These quarantinable VHFs are:

• Lassa fever (LF) virus - an arenavirus
• Crimean-Congo haemorrhagic fever (CCHF) virus - a Bunyavirus
• Ebola virus (EV) and Marburg virus (MV) - filoviruses.

Dengue haemorrhagic fever and yellow fever are discussed elsewhere.

Identification

Clinical features
Clinically apparent infections with any of these viruses may present with similar symptoms. Fever is typically insidious in onset and accompanied by severe headache, myalgia and malaise. Other symptoms include retrosternal chest pain, cough, abdominal pain, diarrhoea, conjunctivitis, facial swelling, proteinuria and jaundice. A bleeding diathesis leads to mucosal bleeding, haematemesis, melaena and haematuria. Severe infections are complicated by massive haemorrhage and multi-organ failure.

Case fatality rates vary greatly:

• Lassa fever virus has a case fatality rate of 1% of infected cases but 25% of hospitalised cases.
• Crimean-Congo haemorrhagic fever virus has a case fatality rate of 2–50%.
• Marburg virus has a case fatality rate of 25% and Ebola virus is 50–90%.

Method of diagnosis
The Department of Human Services and the Victorian Infectious Diseases Reference Laboratory (VIDRL) should be consulted prior to the collection and transport of any clinical specimens from suspected VHF patients for diagnostic testing.

All suspected VHF clinical specimens are tested under the highest bio-security level (BSL–4) laboratory conditions. Diagnosis is typically made using specific PCR tests supported by viral isolation and serology. Appropriate specimens are:

• unclotted blood, tissue or nose and throat swabs for viral PCR
• unclotted blood, urine, tissue or nose and throat swabs for virus isolation
• clotted blood for serology.

Incubation period

The incubation period varies according to the causative agent:

• Lassa fever virus is usually 6–21 days
• Crimean-Congo haemorrhagic fever virus is usually one to three days (range 1–12 days)
• Marburg virus is usually three to nine days
• Ebola virus is usually 2–21 days.

Public health significance & occurrence

The term viral hemorrhagic fever (VHF) refers to a group of rare illnesses that are caused by several distinct families of viruses. While some types of hemorrhagic fever viruses can cause relatively mild illnesses, many of these viruses cause severe life-threatening disease.

Lassa, Marburg and Ebola viruses are restricted to sub-Saharan Africa. Crimean-Congo haemorrhagic fever virus is more widely distributed in Africa, the Mediterranean region, the Middle East, Eastern Europe, Central Asia and China. The origins of the Marburg and Ebola viruses are still unclear but most cases appear to have arisen in Africa.

The high case fatality rate means that it is important that the diagnosis is made and treatment is commenced as early as possible. Viral haemorrhagic fevers should be considered in the differential diagnosis of every patient with an unexplained fever who has been exposed to the infection in an area with endemic VHF during the preceding three weeks.

Reservoir

The reservoir for Lassa fever virus is a rodent known as the multimammate rat of the genus Mastomys spp.

The reservoirs for Crimean-Congo haemorrhagic fever virus are hares, birds and Hyalomma spp. of ticks. Domestic animals such as sheep, goats and cattle may act as amplifying hosts.

The natural reservoir of Ebola virus remains unknown. Current evidence suggests that the virus is zoonotic (animal-borne) and is normally maintained in animal hosts native to the African continent. This could include other primates such as gorillas.

Mode of transmission

Transmission for the viral haemorrhagic fevers depends on the type of virus:

• The Mastomys rodents shed Lassa fever virus in urine and droppings. The virus can be transmitted through direct contact with these materials, touching objects or eating food contaminated with these materials, or through cuts or sores. Person to person transmission may occur through sexual contact or inoculation with blood.
• Crimean-Congo haemorrhagic fever virus is transmitted by the bite of infective Hyalomma spp. ticks. Ticks are believed to acquire the virus by transovarian transmission or from animal hosts. Nosocomial spread to medical workers in contact with infected blood or secretions has been observed. Slaughtering of infected animals is also linked to some infections.
• The source of infection for the index human for Ebola and Marburg viruses is usually unknown. Secondary human infections occur by person to person spread through direct contact with infected blood or secretions, including semen. Nosocomial transmission has also been reported through contaminated needles and syringes.

Period of communicability

Communicability of viral haemorrhagic fevers depends on the infective agent:

• Lassa fever virus is communicable via person to person spread during the acute febrile phase. Virus is excreted in the urine for up to three to nine weeks from the onset of the illness.
• Crimean-Congo haemorrhagic fever virus communicability is unknown. The virus is highly infectious in the hospital setting where it has been transmitted to health care personnel by accidental needle stick injury.
• Marburg and Ebola virus are communicable as long as blood and secretions contain virus. Virus has been isolated in seminal fluid 60 days after the onset of infection.

Susceptibility & resistance

All ages are susceptible. The duration of immunity after infection is unknown.

Control measures

Preventive measures
Not applicable in Australia. No vaccines are available.

Intending travellers to LF and CCHF endemic areas should avoid contact with ticks and rodents.

Control of case
All travellers who arrive in Australia with any risk of contracting quarantinable VHF should be immediately notified to the Department of Human Services.

The Department of Human Services state chief quarantine officer will make any decisions concerning patient’s assessment, transport and quarantine.

All patients should be cared for at the hospital where they are first seen (if possible), or transferred to the Victorian Infectious Diseases Service at the Royal Melbourne Hospital, the designated VHF treatment centre for Victoria, or similarly equipped tertiary hospital.
Intravenous ribavirin may be useful for treatment purposes; a stock of this drug is maintained at a number of tertiary hospitals including the Royal Melbourne Hospital.

Cases should be cared for in an isolation room, preferably with negative pressure ventilation, and non-essential staff and visitors should be restricted. The highest level of barrier infection control precautions should be instituted including gowns, gloves, face shields and masks.

No airborne transmission has been reported so personal and room HEPA filtration is not an absolute requirement but should be used if available. An anteroom for putting on and discarding clothing and storing supplies is advisable.

The obligatory period of isolation for a proven case of viral haemorrhagic fever is a minimum of two days without fever and a total of 21 days from onset of illness.

Convalescent patients and their contacts should be informed that VHF viruses may be excreted for many weeks in semen (MV and EV) and in urine (LF). Meticulous personal hygiene is necessary. Abstinence from sexual intercourse is advised until genital fluids have been shown to be free of the virus.

Post-mortem is discouraged. Bodies of deceased patients should preferably be cremated.

Control of contacts
Active case and contact surveillance is conducted by the Department to identify any fellow cases and all contacts with the patient from the 21 days after the onset of symptoms. A contact is a person who has been exposed to an infected person or to an infected person’s secretions or tissues within three weeks of the patient’s onset of illness.

Contacts are further classified as casual contacts, close contacts or high risk contacts.

Casual contacts are those people with no direct contact with the patient but who have been in the near vicinity, such as on the same aeroplane or in the same hotel. No special surveillance is required although information on the disease and symptoms may be distributed.

Close contacts are defined as those living with the patient, nursing and hugging the patient, or handling the patient’s laboratory specimens. If the diagnosis is confirmed, close contacts are placed under self-surveillance with twice daily recording of body temperature.

High risk contacts are those with a history of either mucous membrane contact with the patient (kissing, sexual intercourse), or needle-stick or other penetrating injuries contaminated with blood or other body fluids from the patient during their infectious period. These contacts should be placed under self-surveillance as soon as VHF is considered to be a likely diagnosis in the index patient.

Any close or high risk contact that develops a fever (> 38°C) or any other symptoms of illness should be immediately isolated and treated as a VHF patient.

Ribavirin may be prescribed as post-exposure prophylaxis for high risk contacts of patients.

Control of environment
All potentially contaminated personal items and items used in the treatment of the patient should be disinfected with an appropriate viricide such as 0.5% hypochlorite or 0.5% phenol with detergent, and as far as possible, subjected to heating by incineration, autoclaving or boiling by appropriately protected staff. Room disinfection should be performed using the same virucidal disinfectants.

These disinfection measures may apply to the patient’s place of residence and other environments where the patient has spent a significant period of time while symptomatic, such as aircraft and hotel rooms.

Outbreak measures

A single case of any of these viral haemorrhagic fevers in any setting would constitute an outbreak and requires the clinical and public health control measures as outlined above.

International measures

In the event of a suspected or confirmed case of any of these viral haemorrhagic fevers, the Department would immediately notify the Commonwealth Chief Medical Officer who would in turn notify WHO according to International Health Regulations, as well as notify the source country and other countries who may receive possible exposure by infected travellers.

Close and high risk contacts should be discouraged from travel during their period of surveillance.

Additional sources of information

• Australian Government Department of Health and Ageing, quarantine and travel health information
• Centers for Disease Control and Prevention, Atlanta USA, Public health emergency preparedness and response