Schistosomiasis (also known as Bilharzia, snail fever, or Katayama fever) is caused by flatworm parasites that live in the blood vessels of the bladder and intestines. Schistosomiasis - also known as bilharzia, snail fever, or Katayama fever - is caused by flatworm parasites that live in the blood vessels of the bladder and intestines. Health Matters
A Tornado warning means A tornado has been  spotted/touched down in your alert area. You should take  cover if a tornado warning is issued for your area;  go into a cellar, or the lowest, most inner part of your house  where there are no windows (a downstairs or basement bathroom is  ideal).
the NWS works closely with communities with severe weather warning systems, including storm sirens. For severe weather, most communities sound sirens anytime a tornado warning is in effect for their area. Other communities have stricter policies and only activate the outdoor warning system for actual tornado sightings, while a few activate sirens for both severe thunderstorm and tornado warnings.