Common problems that travellers encounter, such as stomach upsets and those from insect bites, can be prevented by taking simple precautions.
These include such things as good hygiene and safe food preparation practices, drinking (and using) only treated or clean water, avoiding being bitten by various insects and worms, and getting vaccinated and taking pills to prevent diseases.
Clean water and water treatment
Everyone needs a minimum of about two and a half litres or just over half a gallon of clean water a day. In hot climates while doing things like carrying a backpack, hiking or just walking around in the sun, you will need even more, maybe around 4 litres or about a gallon a day, mainly because of loss from sweating.
It is extremely easy to become dehydrated while travelling in hot and unfamiliar climates. It is recommended to take a water bottle with you each day.
Public water in all of the USA, western Europe and some parts of eastern Europe is safe to drink. A lot of countries around the world, however, are not so stringent about the cleanliness of their water supply, which can mean health risks for travellers.
Drinking water can be contaminated with all sorts of infectious agents, ice (for example, in drinks (even in alcoholic ones)) is a major problem, as is finding safe water to use when brushing your teeth, washing (and swimming).
Salads, vegetables and fruits washed in local water should also be avoided, as well as and water-based products such as ice cream.
Check destination information on the Internet to find out in which countries you are at risk from inadequate sanitation and contaminated water.
Sites such as www.tripprep.com and www.cdc.gov are good sources of information. However, the main danger areas are:
- The Indian subcontinent
- Africa
- Mexico, Central and South America
- Russia and the former USSR countries
- Asia
There are five basic ways to get clean water. Buying bottled water, and either boiling, distilling, filtering or purifying water from local supplies.
Robert Sangster’s book here
Bottled Water
Generally easy to find and sold in various sized plastic bottles. Other bottled drinks are somewhat safe and routinely drunk by travellers.
Bottled water can be expensive, but the main problem, though, is availability. It can’t always be found everywhere you go (or when you want or need it), and even if do find it you can’t be sure that it is really safe. Anyone can fill an old bottle with tap water, reseal it and sell it to you.
The worst thing about bottled water, however, is the hundreds of unrecycled plastic bottles that get dumped or left behind.
Boiling
Boiling water for a minute or two is the best method for eliminating infectious agents. Also the best method to use when making tea, coffee, and soups.
While boiled water is safe, it should not be relied upon as the sole source of drinking water as you won’t always have access to a stove or pan.
Distillation
Distillation involves a unit that boils water and then condenses the steam into a clean container, leaving nearly all of the solid contaminants behind.
This will kill and remove bacteria, viruses, cysts, heavy metals, and other particulates, more so in fact than any other system.
Useful if you can’t tolerate or don’t like the taste of iodine, or for long-term travellers (where using iodine for extended periods may cause problems. See below).
Most systems do need electricity to work, however, although there are some non-electric systems out there. They are also quite slow to produce clean water, as well as being heavy and bulky.
They also leave scale behind, which means that the distillation apparatus be frequently cleaned.
Filtration
Water filtration devices work by forcing water through materials which screen out particles. What gets filtered out depends on the size of the pores in the material used.
Filters of about 0.2 microns will remove dirt, bacteria and parasites, but waterborne viruses, such as hepatitis and polio, are 0.04 microns or smaller so may not be removed, and the water will need subsequent boiling or chemical treatment.
Filtering doesn’t change the taste of the water, however, and there is no need to wait. You can clean and reuse filters so it is also cheap.
Again this is a good solution if you are sensitive to iodine or where viruses might not be a problem, such as for backcountry use in the U.S. and Canada. Also can be used where the user has had all the vaccination for local viruses.
Mechanical filters can, however, be bulky, heavy, and hard to use for less experienced travellers. Filters can become clogged and if further chemical treatment is needed the cost per gallon increases.
Purification
Water can be purified with one of a number of chemical additives. The most popular is iodine, either in tablet or liquid form. Chlorine and silver are alternatives.
Iodine is used by putting 2-3 drops or a couple of tablets in water and letting it stand for about 30 minutes.
The dosage must be doubled for very cold water (e.g. from mountain streams).
Tablets and liquids are very compact and are good for short-term use or with filters.
Regular iodine stains badly (if it leaks in your bag) but you can find uncoloured (as well as regular) iodine in some places, for example, in pharmacies around the world.
With iodine the water has a chemical taste (as it does with chlorine) which some find objectionable, and is coloured, although both the colour and taste can be removed by adding vitamin C (orange juice, for example) to the water, but only after the waiting period is over, otherwise the iodine will be neutralised.
There is some debate over the safety of iodine for long-term use and what is a safe maximum dose to ingest over and above the recommended daily amount. Reports of serious side-effects are few and far between, however. A 1998 study published in the Lancet described thyroid problems in a group of Peace Corps workers in Africa which was linked to their use of two-stage iodine-resin filters as their only water purification method for over two years. Then again a study in the 1960′s of Florida prison inmates who were given iodinated water for up to 15 years showed no such problems. Those with thyroid problems, pregnant women, or those with a sensitivity to iodine, might want to consider alternative solutions, however.
Read more about it here, especially the ‘Recommendations for Iodine Use in Water Treatment’ section.
Other approaches
A combination of methods works well. Some travellers (including myself) carry personal water purifiers which both purify and filter the water at the same time, and generally does it a lot quicker than with iodine alone.
Most purifiers use iodine as the active ingredient as part of a filter cartridge. The filtration process removes the larger, hard-shelled creatures such as Giardia and Cryptosporidium, then the water passes through an iodised resin bed, where bacteria and viruses are deactivated. Some systems incorporate a carbon filter at the final stage of purification. These filters absorb traces of residual iodine and greatly improve the flavour of the water.
The most convenient method I have found so far, and one which I thoroughly recommend, is the 
Aquapure Traveller Water Bottle
As a backup I also carry a 
Steripen buy them in the UK
Another device (used by the US military), is MSR’s MIOX Purifier which creates a dose of mixed oxidants (MIOX) that is then added to the water to inactivate bacteria, Giardia and Cryptosporidium, (which iodine won’t kill). It runs on common camera batteries and uses regular salt to operate, and needs no maintenance.
