I have the same kind of filter as as harrydog, the Katadyn filter that weighs about a pound, a pound and a half. Both it and the smaller Katadyn use ceramic filters, down to .2 microns, IIRC. The larger one lasts much longer, pumps faster, and weighs more - you pays your money and you takes your chances. (I enjoy taking mine apart and feeling the really smooth disassembly screws.) If I were doing it again, I'd buy the smaller one, unless I had to pump for more than one person. There are easier pumping systems on the market. These are the "tactical" versions of water filters, and the larger is/was NATO/STANAG (standard). This was in my luggage while in the Middle East. For shorter term suituations, the lighter duty Sweetwater is very well thought of, though I've never owned one.
I've never carried any iodine pills for purifying water, since the iodine crystals are so easy to own. It's a little two-ounce plastic bottle with iodine crystals inside and a basic temperature gauge strip on the outside. You fill the bottle with water and let the solution super-saturate, then add an amount of the solution to a canteen based upon the temperature and turbidity of the water. It lasts much longer and treats much more (tens? hundreds? of times as much) water as the same size pill bottle. It stores basically forever, also. This was in my hand-carry while in the Middle East.
The .2 micron filter size is a good general use factor. It'll stop flukes and cysts (giardia), but not viruses. I think the iodine will get them, though. Iodine alone will not penetrate cysts unless it's approximately twice the normal strength, again IIRC. Unless you're allergic to it, that shouldn't be a problem, however.
I'd consider the cleaning factor, also. The Katadyn's, at least, pump in such a fashion as to allow you to scrape any micro-cootie (technically speaking) crud off of the outside of the filter element ceramic after you remove it from its casing. Ensure you don't have to clean the inside of anything, since that's harder to get clean.
I'd avoid anything like the "First Need" filter, which is a "depth filter." It uses activated charcoal. The charcoal cleans the micro-cooties out okay, but it leaves them buried in the nice warm, wet filter case, just waiting for the next serving of water to come through. Yuck - putting new water in contact with cooties then trying to re-clean it is a big turn-off, Bob. Also, depth filters tend to clog (like any filter), then if you push the plunger harder to compensate, hydraulic pressure forces the plastic walls away from the charcoal, (possibly) allowing water to flow outside of the filter mechanism. There are so many better ways to do this that I wouldn't even use one of these as a backup to a backup.
For really hard-core survival (as opposed to your trip), there's always a solar still. It's a little hard to carry and slow to use in the PRC, however.
The filter alone always worked for me, that and the bottled water. Make sure waiters and the like open the sealed bottled water at your table. Sometimes they like to save a little money by filling bottled water up at the faucet.
Water isn't your only problem, however; the food is also an issue. Don't eat any leafy green vegetables (think about their fertilizing mehods), and peel fruit yourself. Don't eat cheeses or cream sauces (I'm speaking from experience, here.) Icecubes in drinks? - be paranoid.
Expect some stomach discomfort, just based upon new food and drink that isn't familiar. It doesn't have to be dysentery when you're doing the "two-step" to the nearest facility. Carry your own TP - nothing bad, just sometimes there isn't any when you need it. Carry PeptoBismol in tablet form, and a lot of it, from home. Whatever you do, DO NOT USE Lomotil, what we used to refer to as the "little white stopper." Lomotil is effective in stopping the trots, but, just to be graphic for a second, think about it. If your body wants to get rid of something that badly, why do you want to keep it inside? At worst, you could have some form of cootie that would drill through your colon and cause peritonitis, something I don't want in a US hospital, let alone some other country's.
Consider a hepatitis C injection, just before going.
Well, thus concludeth "Travel Hygiene 101."
Jaywalker
