Yellow Fever - Diagnosis & Differential Diagnosis

In order to make a yellow fever diagnosis, your doctor will ask questions about a number of things (including recent medical and travel history), perform a physical exam, and recommend certain tests. As part of diagnosing a yellow fever virus infection, the doctor will also rule out other more common causes of possible yellow fever symptoms, such as the flu or the common cold. If the doctor thinks a person is at risk for yellow fever, he or she can order certain tests. These tests can include Blood tests, Cerebrospinal fluid tests (CSF), Electrocardiograms (EKGs). These individual tests will not definitely diagnose yellow fever, but they can be helpful. To make a definitive diagnosis of yellow fever, the doctor will draw a blood sample and send it to a commercial or public health laboratory for confirmation. (1)
The diagnosis of yellow fever is made through examining the blood using various techniques in order to demonstrate the presence of either yellow fever viral antigens (the part of the virus that initiates the patient's immune response) or specific antibodies (the cells produced by the patient's immune system that are specifically directed against the yellow fever virus). (2)
Specific diagnosis depends on isolation of virus from blood, demonstration of viral antigen in serum by enzime-linked immunosorbent assay ( ELISA ) or of viral RNA by polimerase chain reaction ( PCR ) during the period of infection. Serologic diagnosis include IgM antibody-capture ELISA, hemagglutination inhibition (HI), complement fixation (CF) or neutralization (N) tests. It’s important to consider that IgM, HI and N antibodies appear within 5 - 7 days and CF antibodies within 7 - 14 days after onset. Thus, paired acute and convalescent sera should be tested ( interval of 14 days ). (3)
Common Differential Diagnosis
Leptospirosis: Increased erythrocyte sedimentation rate, total WBC elevated with neutrophilia and trans aminases levels slightly elevated .
Dengue fever: Indistinguishable from yellow fever in the initial stages; jaundice is, however, a rare sign.
Malaria: It must be always excluded by serial blood examination, even when the diagnosis of yellow fever is confirmed, due to the possible concomitant of both diseases. Anemia without hemorrhagic manifestations, splenomegaly and low levels of transaminases take account of malaria.
Hepatitis: The insidious onset, usually without renal disease ( suggestive ) + presence of viral markers of hepatitis in sera confirm the diagnosis. (3)

References:

1. http://virus.emedtv.com/yellow-fever/yellow-fever-diagnosis.html (accessed July 2010)

2. http://science.jrank.org/pages/7444/Yellow-Fever-Diagnosis.html (accessed July 2010)

3. http://www.medstudents.com.br/dip/dip2.htm (accessed July 2010)

All information provided by Dr Gaurav Gupta, MD, Charak Clinics. Stamaril, Yellow Fever Vaccine is available at Charak Clinics, Chandigarh, North India for all travelers to Endemic Countries in Africa / Central & South America with WHO certificate of vaccination valid for 10 years. For details write to us at drgaurav-at-charakclinics.com (replace -at- by @) or call at 91-172-5092585, 91-9872303775 during Office Hours.