This scanning electron micrograph (SEM) depicts a number of Vibrio parahaemolyticus bacteria; Mag. 19058x. Vibrio parahaemolyticus is a bacterium in the same family as those that cause cholera. It lives in brackish saltwater, and causes gastrointestinal illness in humans. V. parahaemolyticus is a halophilic, or salt-requiring organism, naturally inhabiting coastal waters in the United States and Canada, and is present in higher concentrations during summer. When ingested, V. parahaemolyticus causes watery diarrhea often with abdominal cramping, nausea, vomiting fever and chills. Usually these symptoms occur within 24 hours of ingestion. Illness is usually self-limited and lasts 3 days. Severe disease is rare and occurs more commonly in persons with weakened immune systems.