Beware of Crimean-Congo haemorrhagic fever

Spread by bont-legged ticks, this zoonotic disease can prove fatal to humans if left untreated.

Viral haemorrhagic fever is a zoonotic disease that disturbs blood clotting, so that patients develop haemorrhaging (uncontrolled bleeding). Here are some frequently asked questions about the disease:

• What is it?

Crimean-Congo haemorrhagic fever (CCHF) is a tick-borne viral zoonosis that occurs in Africa, Eastern Europe and Asia.

• How is it transmitted?

The virus is transmitted by bontlegged ticks (Hyalomma spp), which have distinctive brown and white bands on their legs. The virus can remain in the ticks for a long period, and even pass through the eggs to infect the next generation of ticks.

Immature Hyalomma ticks (larvae and nymphs) feed on ground birds such as guinea fowl and small mammals up to the size of hares. Adult ticks feed on livestock such as cattle, sheep, goats and ostriches, as well as wild animals such as antelope. Animals bitten by infected ticks do not develop the disease, but can circulate the virus in their blood for up to a week, and thereafter become immune to further infection.

Non-infected ticks become infected if they feed on the animals when the virus is in circulation.

• How do humans become infected?

Humans can become infected by being bitten by infected ticks, or even from squashing ticks if fluid from the ticks gets into cuts and wounds in the skin or onto mucous membranes. Fortunately, immature ticks feed only on small animals and do not bite humans. Adult ticks prefer farm animals and so seldom bite humans.