Death usually is attributed to cardiovascular depression, respiratory depression, or hypovolemic shock. Most morbidity is neurological. Neurologic symptoms resolve after 1-2 weeks, although pain, paraesthesia, pruritus, and weakness may persist for several weeks. Symptoms increase following ingestion of animal proteins. Chronic symptoms may occur and result in permanent nerve damage.
Several reports show correlation between ethnic backgrounds and common symptom groupings.
Children seem more severely affected and more often involved in life-threatening cases. Diagnosis currently is based on a constellation of symptoms that temporally relate to the ingestion of fish or fish products. Onset of symptoms usually occurs within 2-30 hours, with a mean of 5 hours. Symptoms increase in frequency and severity over the next 4-6 hours. GI symptoms often appear first and can last 1-2 days.