Background to the guideline

About viral haemorrhagic fevers (VHFs)

VHFs are a group of rare illnesses 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. EVD, LF, MVD and CCHF 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. They are therefore subject to biosecurity measures as per the Biosecurity Act 2015.

Other VHFs that are less commonly transmissible between humans but are notifiable include:

• Severe Fever with Thrombocytopaenia Syndrome (SFTS) caused by the SFTS virus
• Argentine haemorrhagic fever (AHF) caused by the Junin virus
• Lujo haemorrhagic fever (LUHF) caused by the Lujo virus
• Bolivian haemorrhagic fever (BHF) caused by the Machupo virus
• Andes haemorrhagic fever (ANDV) caused by the Andes virus (a rodent-borne hantavirus).

Table 1. Key VHFs where human-to-human spread may occur

Note. Adapted from Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) guidance^{1, 2, 3, 4}

Clinical symptoms

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
• signs that include 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.⁵

Epidemiology and public health significance

LF, MVD and EVD viruses are restricted to Sub-Saharan Africa, where most human outbreaks have occurred. CCHF virus is more widely distributed in Africa, the Mediterranean region, the Middle East, eastern Europe, Central Asia and China. The origins of MVD and EVD viruses are still unclear, but most cases appear to have arisen in Africa.

Lassa virus is endemic in West African countries, such as Nigeria, Sierra Leone, Liberia and Guinea, with seasonal outbreaks and ongoing transmission linked to rodent exposure.⁶ EVD and MVD typically emerge in Central and East Africa, often associated with contact with infected wildlife or human-to-human transmission in health care or community settings.⁷

Several recent outbreaks have highlighted the ongoing threat posed by VHF. In early 2025, Uganda faced a Sudan virus (Ebola species) outbreak with 14 cases and four deaths, ending in April 2025.⁸ At the same time, the Democratic Republic of the Congo reported a deadly Ebola virus (Zaire strain) outbreak with 31 deaths out of 38 cases, prompting targeted vaccination using the Ervebo® vaccine.

MVD outbreaks in Tanzania and Rwanda also caused multiple deaths, with Tanzania reporting a 100% fatality rate among 10 cases in an outbreak declared in January 2025, highlighting the critical need for rapid response.⁹

Although CCHF and LF have not seen large-scale international outbreaks recently, both continue to cause sporadic cases and small outbreaks in endemic regions, particularly in West Africa for LF and Eastern Europe, Central Asia and parts of the Middle East for CCHF.¹⁰ Given the high case-fatality rates associated with these diseases, early diagnosis and prompt supportive treatment are critical to improving patient outcomes and preventing secondary transmission, especially in health care settings.

VHF should be considered in the differential diagnosis of any patient presenting with unexplained fever who has travelled to or resides in an area where VHF is endemic within the past 21 days. While there is now an approved vaccine for Ebola virus (Zaire strain), there are currently no licensed vaccines for LF, MVD, Sudan virus or CCHF.

Mode of transmission

The transmission of VHF varies by virus type. People can become infected with Lassa virus via exposure to food or household items contaminated with urine or faeces from infected Mastomys (a genus of rodent in the family Muridae endemic to Africa) or directly via contact with infected rats.

Lassa virus can also spread from person to person through direct contact with blood, urine, faeces or other bodily secretions of someone infected with Lassa virus.

CCHF virus is mainly transmitted by Hyalomma spp. tick bites or contact with infected animals, with nosocomial spread also reported.

For Ebola and Marburg viruses, the initial source is often unknown, but secondary transmission occurs through direct contact with infected body fluids or contaminated medical equipment.

Notes

¹ Centers for Disease Control and Prevention. (2025). Viral hemorrhagic fevers (VHFs)

² World Health Organization. (2025). Ebola virus disease

³ World Health Organization. (2025). Marburg virus disease

⁴ World Health Organization. (2025). Crimean-Congo haemorrhagic fever

⁵ Victorian Department of Health. (2025, June 11). Viral haemorrhagic fevers

⁶World Health Organization. (2024, December 5). Lassa fever

⁷ World Health Organization. (2025, April 24). Ebola disease

⁸ World Health Organization. (2025, April 15). Disease Outbreak News: Uganda Sudan virus outbreak ends

⁹ World Health Organization. (2025, February). Marburg virus disease – Tanzania and Rwanda outbreaks 2025

¹⁰ Centers for Disease Control and Prevention. (2023, December). Crimean-Congo hemorrhagic fever (CCHF) factsheet