Symptoms, transmission, origins… Four questions about Crimean-Congo hemorrhagic fever, detected for the first time in France

This virus is potentially, although rarely, fatal to humans. It was detected for the first time on ticks attached to cattle in the Pyrénées-Orientales.

The presence of the Crimean-Congo hemorrhagic fever virus, CCHF, has just been confirmed for the first time in France by health authorities, such as ANSES. CIRAD, the Center for International Cooperation in Agricultural Research for Development, located it in the Pyrénées-Orientales on October 6. This virus is carried by ticks of the Hyalomma species collected from cattle in the Pyrénées-Orientales. No human cases have been recorded in France, but health authorities are concerned about its possible spread.

What are the symptoms ?

FFHC is a disease caused by the virus of the same name. In humans, the infection generally causes mild symptoms, which are limited to a flu-like syndrome with digestive problems. But in certain cases, the disease can worsen and cause hemorrhaging and failure of vital organs and lead to death in 30% of cases, details the Pasteur Institute.

CCHF is one of the “mandatory reportable” human diseases along with other viral hemorrhagic fevers, such as Ebola. It is therefore subject to extreme surveillance which must be immediately declared to the public health authorities, in order to implement control measures or preventive actions as quickly as possible.

This disease was first discovered in Crimea in 1944, on the shores of the Black Sea. It was then linked to an identical pathology circulating in Congo, which explains its name “Crimean-Congo hemorrhagic fever”.

How is it transmitted?

Contamination by the CCHF virus occurs in most cases through the bite of Hyalomma ticks which are themselves infected. The Hyalomma tick is twice as big as a classic tick, and is recognizable in particular by its two-colored legs.

In addition to tick bites, the disease can also be caught through contact with blood or fluids from contaminated humans or animals. The virus is not transmitted by air, nor by ingestion of raw milk dairy products, reassures the Pasteur Institute.

Where does the FFHC come from?

Crimean-Congo hemorrhagic fever is therefore mainly transmitted by the Hylomma tick. Native to Africa and Asia, this tick is carried mainly by migratory birds. It has been present for several decades in Corsica and since 2015 on the Mediterranean coast. The FFHC virus circulates particularly in Spain.

Around ten indigenous human cases of CCHF have been reported in Spain since 2013, some of which caused the death of the patient., indicates ANSES, the National Health Security Agency. “In France, although the FHCC virus was detected for the first time on ticks collected from cattle farms in the south of the country in 2023, no indigenous human cases have been observed to date.continues ANSES.

Should we be worried?

Human beings are rarely bitten by the Hyalomma tick. In fact, this large tick has no particular appetite for humans and is easily spotted, because it is more visible due to its size. In addition, the Hyaomma tick prefers dry climates and warm periods, unlike other ticks which prefer forest areas. This is why, in France, Hyalomma ticks have until now been found mainly in the scrubland or Mediterranean scrub.

Even if no indigenous cases have yet been detected in humans in France and although FFHC is generally not very symptomatic, “in certain cases, it can worsen and result in a hemorrhagic syndrome, the fatality rate of which reaches 30% in certain countries”, recalls Anses. And an emergence in France is possible, underlines the agency in a report last May. The risk of occurrence of Crimean-Congo fever in France is “all the more likely as the geographical extension of the tick implantation zone should be favored by climate change”warns Elsa Quillery, coordinator of the Anses report.

The agency is calling for Hyalomma ticks to be placed under nationwide surveillance. Because “unlike what exists for mosquitoes, no national surveillance system is organized for ticks even though they transmit serious diseases such as CCHF, but also Lyme disease or tick-borne encephalitis”, underlines Elsa Quillery. ANSES also calls “to develop research” around this tick and this virus, in particular to find a vaccine against Crimean-Congo hemorrhagic fever which does not exist to date.

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