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Rift Valley Fever Outbreak, Saudi Arabia, 2000

On 2/06/1421 H King Fahad Central Hospital in Jazan began receiving several cases of unexplained hemorrhagic fever. At that time, the cases were localized to AlArda district in Jazan region. The clinical picture included low grade fever, abdominal pain, body ache, vomiting and diarrhea, jaundice with liver and renal dysfunction often progressing to disseminated intravascular coagulation, hepatorenal syndrome, and death. The diagnosis of Rift Valley Fever (RVF) was confirmed.
This study was conducted during the period from 27/05/1421 to 30/01/1422 H, to identify the extent and severity of the outbreak; and to study the clinical presentation and complications of the disease. A Case definition was developed and distributed to all hospitals and primary health care centers to detect further cases and report them by completing a case report form, which included identification and demographic data, hospitalization, clinical history, history of contact with an RVF case, positive family history, history of exposure to environmental risk factors, results of laboratory investigations, clinical status, and complications. This form was then sent to the regional health directorate, and on to the Ministry of Health in Riyadh within 24 hours, to be entered into the computer and analyzed.
The total number of patients was 882; 747 (85%) Saudis, 113 (13%) Yemenis, and 22 (2%) other nationalities; 709 (80%) males and 173 (20%) females, the male to female ratio was (4:1). The mean age (± SD) was 45.7 (+ 20) years. Forty seven percent (47%) were reported from Jazan, 48% from Asir, 4% from Qunfudha, and the rest from other regions.
The total number of cases increased gradually from the first week, when only 5 cases were reported, reaching the maximum on the fourth week with 93 reported cases, then fell gradually until the eighth week with 56 reported cases. After that, the number of cases increased again to reach the highest peak on week 10 with 99 reported cases. The cases started to fall again until the end of the outbreak, when the last case was reported on week 28 (Fig 1).
Symptoms of the acute illness were mainly fever (91%), nausea (58%), vomiting (51 %), abdominal pain (39%), and diarrhea (24%).
Blood investigations revealed that 218 patients had a platelet count <100000 mm3 (mean ±SD = 132.8 ±89.5), 88 had hemoglobin < 8g/dL (mean ±SD = 11.34 ± 3.12), 231 had WBC <3/dL. About 90% of the patients had AST and ALT more than 3 times normal, 90% had LDH more than 2 times normal, 30% had CPK more than 2 times normal, 16% had creatinine >150 Umol/L and 15% developed Jaundice with high bilurobin.
Sixty-six percent (66%) reported direct contact with animals and 98% reported exposure to mosquitoes. The total number of deaths was 124, revealing a case fatality rate (CFR) of 14.1%.
Hemorrhagic complications were the most common, developing in 49 cases (7.6%). Hematemesis occurred in 25 (51%), puncture site bleeding in 14 (29%), and melena in 12 (25%). The total number of deaths among patients with hemorrhagic complications was 32 (65%). Symptoms of encephalitis appeared in 110 (18%) patients. The most common neurological manifestations were confusion in 48 (44%), lethargy in 43 (39%), disorientation in 40 (36%), coma in 21 (19°/0) and vertigo in 20 (18%) patients. The total number of deaths among patients with neurological complications was 60 (55%). Visual complications developed among 13 patients (2%). the most common were visual loss in 10 and scotomas in 3 patients.

Editorial note:

Since the discovery of RVF in 1931,[1,2] the disease was seen to spread across most African countries. It moved outside Africa for the first time during this outbreak, which was also recorded in Yemen. It is thought to have entered Saudi Arabia either through infected animals imported to Jazan region, or through infected mosquitoes carried by the wind.[3]
The epidemic curve showed two peaks; on week 4 and week 10, which may be related to the difference in timing of the start of the outbreak between Jazan and Asir regions.
Blood manifestations of thrombocytopenia, anemia, and low prothrombin and thrombin time are common in all RVF outbreaks, and are typical of hemorrhagic fever.[2,4] Liver enzymes were very high due to severe hepatocellular necrosis, and creatinin was high due to renal failure, which are known complications. [2,4] The high CFR of 14% is compatible with a reported CFR of 15% among hospitalized patients in the RVF outbreak in Egypt.[5]
Hemorrhagic complications developed in 7.6%, which is very high compared to previous reports of 1%. However, this percentage only represents severe cases that had presented to hospitals. The death rate was very high among this group (67%), which is higher than previous reports of 50%.[4] Furthermore, encephalitis occurred in 18%, which is much higher than previous reports of 1%. [5] Visual complications occurred in 2% which is similar to previous reports.[5]
  1. Sall AA, De Zanotto PM. Origin of 1997-98 Rift Valley Fever Outbreak In East Africa. Lancet 1998; 352 (9140): 1596-7.
  2. Zeller HG. Enzootic Activity of Rift Valley Fever Virus in Senegal. Am J Trop Med Hyg 1997; 56(3): 265-72.
  3. Sellers RF, Pedgley DE. Rift Valley Fever in Egypt 1977, Disease spread by wind-borne insect vector. The Veterinary Record 1982; 110: 73-77.
  4. Chen JP, Cosgriff TM. Hemorrhagic Fever Virus-induced changes in hemostasis and vascular biology. Blood Coagulation and fibrinolysis 2000; 11: 461-83.
  5. Siam AL,Meegan JM. Gharbaw KF. Rift Valley Fever Ocular Manifestations: observations during the 1977 epidemic in Egypt. Br J Opthalmol, 1980; 64: 366-74.