Criteria – all of the following:
(1) unexplained illness > 48 hours in duration
(2) one or more clinical or laboratory findings (see below)
(3) one or both serologic findings
Clinical or laboratory findings:
(1) clinical jaundice
(2) ALT, AST or GGT level > 3 times the upper limit of normal reference range
(3) abortion (in pregnant woman)
(4) hemorrhage (petechiae, purpura, ecchymoses, oozing from puncture sites, epistaxis, menorrhagia, gastrointestinal bleeding)
(5) neurological findings (vertigo, confusion, disorientation, convulsions, lethargy, asterixis, coma)
(6) (fever, diarrhea, nausea, vomiting or abdominal pain) AND one of the following:
(6a) hemoglobin < 8 g/dL
(6b) platelet count < 100,000 per µL
(6c) LDH > 2 times the upper limit of reference range
(6d) CK > 2 times the upper limit of normal
(6e) creatinine > 150 µmol/L
(7) unexplained death preceded by fever in 2 weeks prior to death
Serologic findings:
(1) positive antigen test
(2) positive IgM antibody in a specimen collected at least 7 days after onset of illness
where:
• The interpretation of absent antibody should not be made on samples collected less than 7 days after disease onset.
• Animals (typically sheep and goats) may be affected as well. Diagnosis in animals can provide supportive evidence for disease in humans.
• Fever is not required for diagnosis.
• The criteria could be modified to include travel or residence in an area where Rift Valley Fever is endemic or possible.
• I am not sure if there needs to be an upper limit on the length of illness, although this could be hard to define in a person with neurologic or renal sequelae.
• Epidemic outbreaks are usually preceded by high rainfall or other conditions favoring breeding of mosquitoes.
