A 40 y.o. marathon runner in San Diego presents with a rash.

He has been training for a marathon

The picture below is a clue to the diagnosis

This is a corvid

Our patient had West Nile virus.  The reservoir of WNV is in birds.  Corvids, the bird family containing crows and jays, are the most susceptible to the virus  and are often found dead when an outbreak occurs. 

While most people contract west nile from a mosquito bite, it can be transmitted in organ transplants and breast milk.  80% of people with West Nile virus are asymptomatic but   10% get a maculopapular rash. Fever and myalgias are also common.  One per cent develop neurologic signs which can be either central as in encephalitis or peripheral, a polio like illness affecting the anterior horn cells.  The latter can present with paralysis of a limb and may be confused with a stroke. In the unfortunate 1% that develop CNS disease, the outcomes are poor.  Cranial nerve palsies, confusion, tremor and brainstem lesions can develop  In those who are severely immune suppressed, there is a 70% mortality. The treatment is supportive care. 

Testing

IGM antibodies may not be immediately positive and retesting is suggested in 8 days.  IgG will stay positive for an extended period. 

If WNV is suspected in  an immunosuppressed patient IgM in CSF may be negative.PRNT( plaque reduction neutralization tests) are recommended. in confusing cases since other flaviviruses can also be postive.

FUN FACT

West Nile virus is named after the West Nile district of Uganda where the virus was first isolated in 1937.

cases by state in 2024

Kapadia R et al. Severe arboviral neuroinvasive disease in patients on rituximab therapy. Review Clin Infect Dis 2022 doi:10,1093/cid/ciac 766

Center for disease control and preventionWest Nile reported to CDC by week of illness 1999-2021. https://www.cdc.gov/westnile/stats maps/

https://www.medscape.org/viewarticle/990058_2