West Nile fever in humans is a notifiable disease at the European Union (EU) level according to Commission Decision 2009/312/EC.
The case definition for reporting human cases of West Nile fever at EU level is outlined in Commission Decision of 28/IV/2008.
It includes the following criteria and case classification:
Any person with fever OR
at least one of the following two:
1. Laboratory test for case confirmation
At least one of the following four:
- Isolation of WNV from blood or CSF
- Detection of WNV nucleic acid in blood or CSF
- WNV specific antibody response (IgM) in CSF
- WNV IgM high titre AND detection of WNV IgG, AND confirmation by neutralisation
2. Laboratory test for a probable case
WNV specific antibody response in serum. Laboratory results need to be interpreted according to flavivirus vaccination status.
At least one of the following two epidemiological links:
- Animal to human transmission (residing, having visited or having been exposed to mosquito bites in an area where WNV is endemic in horses or birds)
- Human to human transmission (vertical transmission, blood transfusion, transplants)
Any person meeting the clnical criteria AND with at least one of the following two:
- an epidemiological link
- a laboratory test for a probable case
Any person meeting laboratory criteria for case confirmation.