People who have had an organ or bone marrow transplant and are taking anti-rejection drugs. Your doctor can tell you if the precautions described here apply to you. Drinking water Most of British Columbia's drinking water comes from surface sources, such as rivers, lakes and streams, which are easily contaminated by animal faeces.
Surface water can contain a number of different bacteria, viruses and parasites.
If your immune system is weakened, any of these organisms can make you sicker than they would if your immune system was working normally. If your immune system is weakened, you should not drink water directly rom rivers, creeks, lakes or other surface water sources. You should also try not to swallow surface water while swimming or doing other recreational activities in or on lakes, rivers, etc. You should not drink water out of the tap or use tap water for tooth brushing or mouth rinsing without boiling it first. Ice cubes made from unboiled tap water can also carry these organisms.