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).
It does not mean tornadoes are imminent, just that you need to be alert, and to be prepared to go to safe shelter if tornadoes do happen or a warning is issued. This is the time to turn on local TV or radio, turn on and set the alarm switch on your weather radio, make sure you have ready access to safe shelter, and make your friends and family aware of the potential for tornadoes in the area.