Viral haemorrhagic fevers

Viral haemorrhagic fevers (VHFs) include various diseases (Ebola, Lassa fever, Marburg fever, Crimean-Congo fever, etc)

Last updated on 19 June 2024

In brief

Viral haemorrhagic fevers (VHFs) include various diseases (Ebola, Lassa fever, Marburg fever, Crimean-Congo fever, etc) which have certain symptoms in common: high fever, muscle and joint pain, bleeding, diarrhoea and vomiting… These diseases can be serious (average fatality rate of 1% for Lassa fever, 50% for Ebola and Marburg haemorrhagic fever, and 30% for Crimean-Congo fever).

Viruses from different families (Filoviruses, Hantaviruses, Arenaviruses, etc.) can cause viral haemorrhagic fevers. They are transmitted through contact with carrier animals (carcasses or fluids of contaminated animals, for example for Ebola, Lassa or Marburg fevers), insect bites (mosquitoes, ticks for Crimean-Congo and Rift Valley fevers) and human transmission (blood, secretion, etc.).

Following the 2015 Ebola epidemic in West Africa, which led to over 29 000 cases of illness and around 11 000 deaths, the unprecedented mobilisation of the international community has highlighted the need to implement effective coordination structures to be better prepared for viral haemorrhagic fever epidemics that pose a threat to global public health because of their epidemic potential and/or lack of or inadequate support: the Ebola, Lassa and Marburg viruses.

Focus on haemorrhagic Crimean-Congo fever

The virus responsible for Crimean-Congo haemorrhagic fever (CCHF) is transmitted by tick bites. CCHF is endemic in Africa, Asia and the Middle East. More recently established in Spain and Italy, ticks of the genus Hyalomma have also been found in the south of France.

CCHF has been under surveillance in France since 2015. In 2023, for the first time in the country, around a hundred Hyalomma marginatum ticks carrying the CCHF virus, belonging to the Nairoviridae family, were detected in the Pyrénées-Orientales region. With a preference for dry, warm climates, this tick has been found from the Spanish border to the Italian border (Pyrénées Orientales, Aude, Hérault, Gard, Ardèche, Drôme, Bouches-du-Rhône, Var, Alpes-Maritimes) and in Corsica. With the detection of the virus and the tick, the risk of infection in France has now been demonstrated.

Larger than other ticks, Hyalomma marginatum ticks are easy to spot, so it is easier to remove them before they settle and gorge themselves. The adult tick bites domestic and wild ungulates. It is active in spring, between April and July. The frequency of human bites is thought to be low.

However, CCHF is not only transmitted by tick bites. It can also be transmitted through contact with infected human or animal blood or fluids . There is currently no effective treatment, which is why prevention is so important. To date, no human cases have been reported in France. In Spain, where the main vector is a different thick (Hyalomma lusitanicumon), one to three cases a year have been reported since 2018.