Facts about Alkhurma haemorrhagic fever
Alkhurma haemorrhagic fever (AHF), caused by the Alkhurma haemorrhagic fever virus (AHFV), is a tick-borne virus of the flavivirus family. The virus was first isolated in Saudi Arabia in 1994 from the blood of a butcher who presented with severe illness after slaughtering a sheep imported from the city of Alkhurma.
AHFV is closely related to the severe tick-borne Kyasanur Forest disease virus that has been reported in India.
Up to 2010 the disease had been reported in south-western Saudi Arabia, in the Makkah and Najran provinces.
AHF presents with acute febrile flu-like illness, headaches, retro-orbital pain, joint pain, generalised muscle pain, anorexia and vomiting with hepatitis. Haemorrhagic manifestations occur in 55% of cases and encephalitis has been observed in 20% of cases. The case fatality rate is 25% of documented cases.
Asymptomatic and mild cases are also suspected.
Reservoir: Currently ticks are the only known vectors. Tick-borne flaviviruses are usually transmitted by hard ticks. However, AHFV viral RNA has been detected in soft ticks (Ornithodoros savignyi) collected at a camel resting place in the city of Jeddah, Saudi Arabia.
No documented animal reservoirs have been reported, but human infections linked to contact with small ruminants (sheep, goats) and camels have been mentioned.
Transmission mode: Transmission is through tick bites and contact with infected blood on a skin wound (e.g. during the slaughter of animals). Consumption of unpasteurised dairy products from infected animals (camels) has also been reported as a mode of transmission.
The incubation period for AHF is unknown, but probably similar to other tick-borne flavivirus infections (i.e. 3–8 days).
Human-to-human transmission has not been documented and the seasonality of transmission is unknown.
Prevention and control of AHFV infection is achieved by avoiding or minimising exposure to infected ticks and to the blood of animals during slaughtering activities, as well as by avoiding consumption of unpasteurised milk.
Direct diagnosis is done through detection of the viral genome by RT-PCR and/or isolation on cell culture (BSL3 or BSL4 agent depending on the country regulations). Serological detection of specific IgM can be performed (possible cross reactions with other flaviviruses).
Management and treatment
As there is currently no vaccine available, addressing symptoms is the only known treatment for AHFV infection.
Key areas of uncertainty
Understanding the cycle of AHFV transmission requires further field investigations. Because of the large livestock trade with neighbouring countries, the spread of the virus to other areas and countries cannot be excluded. As AHF disease is severe, the situation needs to be carefully monitored.
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Charrel RN, Zaki AM, Fakeeh M, Yousef AI, de Chesse R, Attoui H, et al. Low diversity of Alkhumra hemorrhagic fever virus, Saudi Arabia, 1994–1999. Emerg Infect Dis. 2005 May; 11(5):683–8.
Charrel RN, Fagbo,S, Moureau,G, Hussain Alqahtani M, Temmam,S, de Lamballerie X. Alkhumra Hemorrhagic Fever Virus in Ornithodoros savignyi ticks. Emerg Infect Dis. 2007 Jan; 13(1):153-155
Alkhumra hemorrhagic fever virus, March 25, 2009.