Most infected people will never know they have had the disease. Research indicates that only about one out of every five people who are infected with WNV develop symptoms.
West Nile non-neurological syndrome
Most people who develop symptoms will experience varying degrees of an illness known as West Nile Non-neurological Syndrome. Even non-neurological forms of the disease may cause lasting health effects, including muscle weakness, memory problems and fatigue which may continue for months.
The symptoms of West Nile non-neurological syndrome include some or all of the following:
- muscle weakness
- muscle and/or joint aches
- sensitivity to light
West Nile neurological syndrome
In less than one per cent of infected individuals (about one in 150), WNV can cause severe illness resulting in hospitalization. This is called West Nile neurological syndrome and includes swelling of the brain (encephalitis), inflammation of the lining of the brain (meningitis) or paralysis. For people who develop West Nile neurological syndrome, about 10 per cent die.
West Nile neurological syndrome includes some or all of the following symptoms:
- severe headache
- stiff neck
- loss of consciousness
Symptoms begin approximately three to 14 days after being bitten by an infected mosquito. Recovery from symptoms may occur in about a week with West Nile non-neuorological syndrome and may take a year or more for West Nile neurological syndrome.