Assessing the level of suspicion for VHF

Signs and symptoms of most VHFs are non-specific and similar to many other common causes of febrile illness in returning travellers. Because of this, travel history and epidemiological risk factors are critical in determining immediate management, which aims to prevent human-to-human transmission of VHF. A VHF infection is possible in any patient with the clinical and epidemiological characteristics outlined here.

Clinical characteristics

A compatible clinical illness as determined by consultation with an infectious disease physician. Common presenting signs and symptoms include:

• fever (recorded fever ≥ 38° in the previous 24 hours or subjective history of fever in the last 24 hours)
• myalgia
• prostration
• headache
• pharyngitis
• conjunctival injection
• flushing
• gastrointestinal symptoms.

This may be complicated by spontaneous bleeding, petechiae, hypotension and hypovolemic shock, oedema and neurologic involvement.

Epidemiological characteristics

VHF symptoms can appear anywhere from two to 21 days after exposure to the virus, depending on the virus. Illness typically progresses from ‘dry’ symptoms (fever, aches and fatigue) to ‘wet’ symptoms (diarrhoea, vomiting and in some cases, bleeding).¹

A person with EVD, MVD, or LF is not contagious until the appearance of symptoms.^{2, 3} A person can become infected with viruses causing VHF by coming into contact with an infected person’s bodily fluids, contaminated medical supplies and equipment, or contaminated environmental surfaces. Splashes to unprotected mucous membranes (for example, the eyes, nose or mouth) are particularly hazardous.

The epidemiological characteristics that raise the level of suspicion for VHF are that the person:

• reported returning from a specific local area of a country where there is a current VHF outbreak,* with or without direct contact with blood, other body fluids, secretions or excretions from a person or animal with confirmed or suspected VHF

OR

• travelled in or was resident in the specific local area of a country where VHF is endemic** and has recently been reported with one or more exposure risk factors that include:
  • receiving a tick bite or crushing a tick in an area endemic for CCHF
  • visiting caves or underground mines and being exposed to bat colonies or having had direct contact with primates, antelopes or bats in a Marburg or Ebola endemic area
  • living or working in basic rural conditions in an area endemic for LF
  • having persistent fever ≥72 hours, with malaria excluded and no alternative diagnosis apparent
  • having worked in a laboratory or animal facility that handles specimens or tissue contaminated with VHF.

*Information about current VHF outbreaks can be obtained from:

• WHO: Disease Outbreak News
• CDC: Outbreak History (Ebola specifically)
• GOV UK: High consequence infectious disease: country specific risk
• ProMED: Protecting Global Health, One Alert at a Time
• Centre for Infectious Disease Research and Policy (CIDRAP)
• BEACON: Disease Events

**Endemic areas for VHFs include:

• LF – parts of West Africa, including Sierra Leone, Liberia, Guinea and Nigeria
• MVD – the reservoir host of Marburg virus, the African fruit bat, is widely distributed across Africa. Marburg outbreaks have occurred in Uganda, Angola, Kenya, Zimbabwe and the Democratic Republic of Congo
• CCHF – Eastern Europe, particularly in the former Soviet Union, throughout the Mediterranean, in north-western China, central Asia, southern Europe, Africa, the Middle East and the Indian subcontinent.

Notes

¹ Centers for Disease Control and Prevention. (2024, May 9). Clinical screening and diagnosis for VHFs.

² World Health Organization. (2023, August). Infection prevention and control guideline for Ebola and Marburg disease. Geneva: World Health Organization.

³ Centers for Disease Control and Prevention. (2025, January 31). About Lassa fever.