Most common human health problems associated with red tides and other harmful algae blooms are various types of gastrointestinal, respiratory, and neurological disorders. The natural toxins in harmful algae can cause several different illnesses. Most develop rapidly after exposure occurs and are characterized by severe symptoms such as diarrhea, vomiting, dizziness, headaches, and many others. Most people recover within a few days, but some illnesses linked to harmful algae blooms can be fatal.