Facts about Alkhurma haemorrhagic fever

Name and nature of infecting organism

Alkhumra haemorrhagic fever is a viral haemorrhagic disease reported mainly in Saudi Arabia. The virus was isolated in 1994 from the blood of a butcher with a severe illness in Jeddah. This patient became sick after he slaughtered a sheep imported from the city of Alkhumra, Makkah province. Since 1994, about 40 human cases have been confirmed according to published reports.

The aetiological agent is a Flavivirus genetically belonging to the tickborne group that is very closely related to Kyasanur forest disease virus, a severe tick-borne hemorrhagic disease reported in India (Karnataka state).

Geographical distribution

Up to 2010 the disease has been reported in south-western Saudi Arabia, in the Makkah and Najran provinces.

Clinical features

Alkhumra haemorrhagic fever causes acute febrile flu-like illness, headaches, retro-orbital pain, joint pain, generalized muscle pain, anorexia and vomiting with hepatitis. Haemorrhagic manifestations occur in 55% of cases and encephalitis has been observed in 20% of the cases. The case fatality rate is 25% of documented cases.

Non symptomatic and mild cases are also suspected.

Transmission

Reservoir: Currently ticks are the only known vectors. Tickborne flaviviruses are usually transmitted by hard ticks. However, Alkhumra viral RNA has been detected in soft ticks (Ornithodoros savignyi) collected at a camel resting place in Jeddah.

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 (camel) has also been reported as a mode of transmission.

The incubation period for Alkhumra haemorrhagic fever is unknown, but probably similar to other tickborne flavivirus infections (i.e. 3–8 days).

Note: Human to human transmission has not been documented and the seasonality of transmission is unknown.

Prevention measures

Prevention and control of Alkhumra infection is achieved by avoiding or minimising the exposure to infected ticks, to the blood of animals during slaughtering activities and by avoiding consumption of non pasteurized milk.

Diagnosis

Direct diagnosis is done by detection of 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

While there is currently no vaccine available, administering to symptoms is the only known treatment for Alkhumra virus infection.

Key areas of uncertainty

Understanding the cycle of Alkhumra virus 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. Therefore, and taken into account the disease severity, the situation needs to be carefully monitored.

References

Zaki AM. Isolation of a flavivirus related to the tick-borne encephalitis complex from human cases in Saudi Arabia. Trans R Soc Trop Med Hyg. 1997 Mar–Apr;91(2):179–81.

Madani TA. Alkhumra virus infection, a new viral hemorrhagic fever in Saudi Arabia. J Infect. 2005 Aug;51(2):91-7. Comment in: J Infect. 2006 Jun; 52(6):463-4

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.