Viral haemorrhagic fevers

Notification requirement for viral haemorrhagic fevers

Viral haemorrhagic fever is an ‘urgent’ notifiable condition and must be notified by medical practitioners and pathology services immediately by telephone upon initial diagnosis (presumptive or confirmed). Pathology services must follow up with written notification within 5 days.

This is a Victorian statutory requirement.

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

Primary school and children’s services centres exclusion for viral haemorrhagic fevers

Exclude until medical clearance.

Infectious agent of viral haemorrhagic fevers

Four viral haemorrhagic fevers (VHFs) are of particular concern because they could be imported into Australia and be transmitted to other people, particularly healthcare personnel, by blood or body fluid inoculation. The infectious agents for these quarantinable VHFs are:

• Lassa fever (LF) virus – an arenavirus
• Crimean–Congo haemorrhagic fever (CCHF) virus – a bunyavirus
• Ebola virus and Marburg virus – filoviruses.

Dengue haemorrhagic fever and yellow fever are discussed elsewhere.

Identification of viral haemorrhagic fevers

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:

• LF has a case-fatality rate of 1 per cent of infected cases but 25 per cent of hospitalised cases.
• CCHF has a case-fatality rate of 2–50 per cent.
• Marburg has a case-fatality rate of 25 per cent.
• Ebola has a case-fatality rate of 50–90 per cent.

Diagnosis

The department and the Victorian Infectious Diseases Reference Laboratory should be consulted before 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 biosecurity level (BSL 4) laboratory conditions. The document Laboratory precautions for samples collected from patients with suspected viral haemorrhagic fevers should be referred to.

Diagnosis is typically made using specific polymerase chain reaction (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 of viral haemorrhagic fevers

The incubation period varies according to the causative agent:

• LF virus – range is 6–21 days.
• CCHF virus – range is 1–12 days (usually 1–3 days).
• Marburg virus – range is 3–9 days.
• Ebola virus – range is 2–21 days.

Public health significance and occurrence of viral haemorrhagic fevers

The term ‘viral haemorrhagic fever’ refers to a group of rare illnesses that are caused by several distinct families of viruses. Although some types of haemorrhagic fever viruses can cause relatively mild illnesses, many cause severe, life-threatening disease.

LF, Marburg and Ebola viruses are restricted to sub-Saharan Africa. CCHF virus is more widely distributed in Africa, the Mediterranean region, the Middle East, eastern Europe, Central Asia and China. The origins of 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. VHFs 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 3 weeks.

Reservoir for viral haemorrhagic fevers

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

The reservoirs for CCHF 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 is probably African fruit bats. Current evidence suggests that the virus is zoonotic (animal-borne) and is normally maintained in animal hosts native to the African continent. Outbreaks among species such as chimpanzees, gorillas, monkeys and forest antelope occur from time to time.

Mode of transmission of viral haemorrhagic fevers

Transmission of the VHFs depends on the type of virus:

• Mastomys rodents shed LF virus in urine and droppings. The virus can be transmitted through direct contact with these materials, through 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.
• CCHF 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, and sharps injury.

Period of communicability of viral haemorrhagic fevers

Communicability of VHFs depends on the infective agent:

• LF virus is communicable via person-to-person spread during the acute febrile phase. Virus is excreted in the urine for up to 9 weeks from the onset of the illness.
• CCHF virus communicability is unknown. The virus is highly infectious in the hospital setting, where it has been transmitted to healthcare personnel by accidental needlestick 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 and resistance to viral haemorrhagic fevers

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

Control measures for viral haemorrhagic fevers

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.

The State Chief Human Quarantine Officer will make any decisions concerning patient 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 a 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 it 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 VHF is a minimum of 2 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 (Marburg and Ebola viruses) and in urine (LF virus). Meticulous personal hygiene is necessary. Abstinence from sexual intercourse is advised until genital fluids have been shown to be free from the virus.

Postmortem examination 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 3 weeks of the patient’s onset of illness.

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

• Casual contacts are 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 people living with the patient, nursing or hugging the patient, or handling the patient’s laboratory specimens without taking appropriate precautions. If the diagnosis is confirmed, close contacts are placed under self-surveillance, with twice-daily recording of body temperature.
• High-risk contacts are people with a history of either mucous membrane contact with the patient (kissing, sexual intercourse), or needlestick 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 (twice-daily recording of temperature and reporting of illness) 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 per cent hypochlorite or 0.5 per cent phenol with detergent, and, as far as possible, subjected to heating by autoclaving or boiling by appropriately protected staff. Items to be disposed of should be incinerated. 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 for viral haemorrhagic fevers

A single case of any of these VHFs in any setting would constitute an outbreak, and requires the clinical and public health control measures outlined above.

International measures

In the event of a suspected or confirmed case of any of these VHFs, the department would immediately notify the Commonwealth Chief Medical Officer, who would in turn notify the World Health Organization, according to international health regulations, as well as notifying the source country and other countries that may receive possible exposure by infected travellers.

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