Health officials characterize West Nile infections three ways: neuroinvasive, West Nile fever and asymptomatic. A neuroinvasive illness is severe and typically results in a swelling of the brain or spinal cord. People with this illness are at risk of brain damage or death. West Nile fever is less severe, with most people only suffering mild, flu-like symptoms. Asymptomatic individuals were never ill and were only discovered to have the West Nile virus in their blood when blood work was done for some other reason, such as blood donation.