YOU ARE HERE:
Drinking water
On the whole, it’s safe for people with HIV to drink water from the tap in the UK.
But if you have a severely damaged immune system, a little more caution might be needed. Water companies cannot guarantee that water supplies are free from cryptosporidium or other similar organisms which cause diarrhoea in HIV-positive people who have very low CD4 cell counts. Once contracted, cryptosporidium seems impossible to eliminate in HIV-positive people who have CD4 counts below 200 and leads to serious diarrhoea and inability to absorb food or fluids. It is a serious opportunistic infection, against which current treatments are only partially successful.
People who have CD4 cell counts above 200 appear to have developed enough immune response to control cryptosporidiosis, although they may experience some diarrhoea.
There were several outbreaks of cryptosporidiosis in London and Oxfordshire in the early 1990s, which caused severe diarrhoea even in HIV-negative people. These outbreaks have been traced to the water supply.
Thames Water, which provides water in London, says that it is impossible to filter drinking water for the cryptosporidium egg because the infectious dose is so low. Hundreds of gallons of water would need to be screened to find one egg. Unlike bacterial infections, which are able to establish themselves only when tens of thousands of bacteria get into the gut, ten cryptosporidium eggs are enough to cause severe diarrhoea.
If you fit your own filter against cryptosporidium, it should have a very fine mesh.
Filtered water should be kept in the fridge. If it is left at room temperature, it may actually be more vulnerable to bacterial contamination than plain tap water because filtering removes the chlorine which is added to water supplies. The main drawback of filtered water is the cost; over £100 for the filter and fitting.
The only other way to eliminate the organism is to boil drinking water for at least one minute. Such a lengthy boiling period is necessary in order to ensure that all the water has reached boiling point; an automatic kettle switches off when the water in contact with the filament has reached boiling point. Some experts on water safety say that this is not long enough to ensure the elimination of some organisms.
Many people assume that bottled mineral water is always safe, but this is definitely not true. Bottled water sources cannot be screened for cryptosporidium either, and other bacteria not present in chlorinated tap water have been found in some brands of bottled water.
It is important to remember that drinking water includes the water with which you brush your teeth and prepare or wash food (for people with CD4 counts below 200, this means being careful all the time). Drinking water also includes ice in drinks, which is made from tap water.
Drinking water may also contain other diarrhoea-causing bacteria. These have been isolated in bottled water as well as tap water, and the only way to remove these bacteria is either to boil water or to use a very fine mesh filter, even finer than the filters recommended for cryptosporidium. Jug filters, which are very popular, tend to remove chemical impurities but may not always screen out bacteria.
To make life easier, it may help to boil up water once a day and keep it in the fridge to use later on. Don't use boiled water that is over twelve hours old, even if it has been kept in the fridge.
Unfortunately, it is not always possible to monitor the quality of water which you drink or which is used in the preparation of food outside the home. In these circumstances, the best policy may be to avoid salads and other raw foods, and to drink bottled water from deep mountain springs, which are least likely to be contaminated with cryptosporidium.
Beer, pasteurised fruit juice and bottled/canned soft drinks do not carry the risk of cryptosporidium infection, but it's unknown whether wine could carry the infection.
Water outside the UK can present problems. Even in other European countries it is best to stick to boiled water or, if this is difficult, bottled water that comes from deep mountain springs. In tropical and subtropical countries, water presents a very serious health hazard to HIV-positive people. A large number of gut infections are water-borne, including some which cause life-threatening diarrhoea, and any traveller who returns from these countries with diarrhoea will tell you that, however tempting it may look, roadside food and drink is not worth the risk.
Swimming in the sea or in rivers may also be inadvisable for people with compromised immune systems, especially off the British coast. Several recent reports have highlighted extensive problems with water-borne infections contracted from polluted or sewage-ridden water. This is also known to be a problem in many Mediterranean resorts and a cautious approach would be to swim only in chlorinated swimming pools.