Rift in the Arabian Peninsula

Abstract & Commentary

Synopsis: The first outbreak of rift valley fever outside of Africa was associated with a high frequency of severe hepatic involvement and acute renal failure.

Source: Al-Hazmi M, et al. Endemic rift valley fever in Saudi Arabia: A clinical study of severe illness in humans. Clin Infect Dis. 2003;36:245-252.

Al-hazmi and colleagues report their experience with 165 patients with rift valley fever admitted to a single hospital in southwestern Saudi Arabia from September through November 2000. Prior direct contact with either infected and sick relatives or with sick, aborted, or dead animals was reported by 60%. Eighty percent reported frequent mosquito bites, and 13% frequently ingested raw milk.

Nausea or vomiting was reported by 92% of the patients, and 74% complained of fever and/or chills. Forty-six percent had abdominal pain, 43% had diarrhea, 41% had headache, 40% had myalgia, and 30% had symptoms referable to the central nervous system. Seventeen percent had hemorrhagic manifestations, and 11% were jaundiced. Hepatomegaly and splenomegaly were detected in 13% and 12%, respectively.

Ninety percent had AST levels > 3 times the upper limit of normal, and 75% of patients had hepatic failure. Renal dysfunction was present on admission in 55%, and one-fifth of the 165 patients required hemodialysis. Retinitis was detected in 10% during hospitalization and was bilateral in the majority. Three of the 16 with retinitis had permanent vision loss. The in-hospital mortality was 34%.

Comment by Stan Deresinski, MD, FACP

Rift valley fever is caused by a Phlebovirus that is usually transmitted by the bite of infected Aedes and Culex mosquitoes, although it may also be acquired by contact with infected body fluids of animals. Symptomatic infection occurs after an incubation period of 3-7 days. Fever, headache, arthralgias, myalgias, and photophobia are the usual initial symptoms. Most cases are self-limited, but, as in the Saudi outbreak, the first identified outside of Africa, the infection may be severe and even fatal. In this outbreak, hepatic involvement was a common element of severe infection.

Rift valley virus is one of many causes of hemorrhagic fever syndrome which, in Saudi Arabia, must primarily be distinguished from Crimean-Congo hemorrhagic fever. Death may also be associated with acute renal failure and with encephalitis, as well as hepatic failure. A characteristic finding, although occurring at a relatively low frequency, is that of macular and perimacular retinitis, a manifestation of a vasculitic process that may lead to permanent blindness. Ribavirin therapy has been reported to be effective in animal models of infection, but its efficacy in human infection is unknown. An inactivated RVF vaccine has been reported to be safe and immunogenic in humans.

Dr. Derenski is Clinical Professor of Medicine, Stanford; Associate Chief of Infectious Diseases, Santa Clara Valley Medical Center.