An investigation of a major outbreak of Rift Valley fever in Kenya: 2006-2007.
An outbreak of Rift Valley fever (RVF) occurred in Kenya during November 2006 through March 2007. We characterized the magnitude of the outbreak through disease surveillance and serosurveys, and investigated contributing factors to enhance strategies for forecasting to prevent or minimize the impact of future outbreaks. Of 700 suspected cases, 392 met probable or confirmed case definitions; demographic data were available for 340 (87%), including 90 (26.4%) deaths. Male cases were more likely to die than females, Case Fatality Rate Ratio 1.8 (95% Confidence Interval [CI] 1.3-3.8). Serosurveys suggested an attack rate up to 13% of residents in heavily affected areas. Genetic sequencing showed high homology among viruses from this and earlier RVF outbreaks. Case areas were more likely than non-case areas to have soil types that retain surface moisture. The outbreak had a devastatingly high case-fatality rate for hospitalized patients. However, there were up to 180,000 infected mildly ill or asymptomatic people within highly affected areas. Soil type data may add specificity to climate-based forecasting models for RVF.
Nguku
Patrick M
PM
Division of Communicable Disease Control, Kenya Ministry of Public Health and Sanitation, Nairobi, Kenya. drnguku@yahoo.com
Sharif
S K
SK
Mutonga
David
D
Amwayi
Samuel
S
Omolo
Jared
J
Mohammed
Omar
O
Farnon
Eileen C
EC
Gould
L Hannah
LH
Lederman
Edith
E
Rao
Carol
C
Sang
Rosemary
R
Schnabel
David
D
Feikin
Daniel R
DR
Hightower
Allen
A
Njenga
M Kariuki
MK
Breiman
Robert F
RF
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000097:blood; D002648:Child; D002675:Child, Preschool; D002980:Climate; D004196:Disease Outbreaks; D005260:Female; D005544:Forecasting; D006801:Humans; D007630:Kenya / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance / Q000379:methods; D012295:Rift Valley Fever / Q000453:epidemiology / Q000401:mortality / Q000517:prevention & control / Q000821:virology; D012296:Rift Valley fever virus / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D012987:Soil / Q000032:analysis; D055815:Young Adult
D000914:Antibodies, Viral; D012987:Soil