Louis,<br><br>Heck, I have no idea. It killed about 100 folks in the US many years ago (late 80s???) - Milwaukee and Texas, IIRC. Got in the municipal water systems. From what I've read, a good chunk of the populace is either immune or asymptotic - no ill effects. At least 40% suffer no ill effects, near as they can figure, although that's hardly gospel. L. giardia, the "more common" oocystic critter, for sure does not adversely affect everyone - that's well documented. Cryptosporodium p. seems to be nastier, but it also seems like it is not very common in the concentration required to infect folks. I'd suggest checking with the Penn Dept of Public Health and see what they say.<br><br>I've been intrigued by the UV pen ever since I stumbled across it a few months ago. There's some 3rd world water treatment techniques I posted a while back that rely on natural UV as the disinfection mechanism - a bit too involved and time consuming for casual use, but UV clearly works well for disinfection. I think the cost of the UV pen is outrageous, though - it's hard for me to believe that they are very expensive to manufacture. The cost is perhaps a reflection of low volume production....? Or it's so new that the early buyers are paying off the R&D sunk costs - I dunno. $200 buys a lot of Polar Pure or iodine tabs... or a really nice filter unit.<br><br>To tell the truth, I don't worry too much about my water. If I had one of those UV pens, I'd use it - I just don't like the cost. Depending on where I am, I often simply drink the water and so far it's never made me sick. If I'm not sure, I use iodine tabs. On a few trips I've used bleach. YMMV, so that's NOT advice!!! I am more concerned about personal hygene than a few cooties in the water - dirty hands and bits of spoiled food on utinsels are FAR more likely to make one sick than most water, IMHO (and experience).<br><br>All there is to go on is the labwork on the UV pen - just like any other water disinfection. IIRC, there are a couple of guys on the forum that have the capability to scientifically test disinfection efficacy, but I'm not one of them!<br><br>I don't know anyone who has one of these devices, but the technology seems to be up to snuff. Sorry I can't be of more help - it's your call. <br><br>Regards,<br><br>Tom