Monday, September 9, 2013
Water and hand sanitization: some thoughts about technology and hygiene and how not to get sick or make other people sick.
Most infectious ills of the gut are transmitted by the fecal-oral route. The bacterium, parasite, virus or other unspecified microorganism must make its way from the feces (or sometimes vomit) of the infected person to the mouth of the new host to be ingested, thence to infect and cause disease. For many conditions it does not take many organisms to cause infection, and some of the causative entities can survive outside of a host in pretty unfriendly environments for various amounts of time (up to around 2 weeks for norovirus, for instance.) After having a bowel movement, the hands are the most adventurous parts of the body, in terms of making contact with other people, and so cleaning the hands is the most vital part of preventing person to person transmission. Water contamination with feces is very common, either from washing or directly depositing the intestinal contents in a place where they can be transmitted by rain or other mechanical means to a water source, or by animals who carry the pathogenic organisms pooping wherever the mood hits them. Thus purification of water is key to preventing the spread of infectious gastroenteritis.
In hospitals hand hygiene is often a matter of life and death. In the years before Ignaz Semmelweis instituted hand sanitization with a cholorinated lime solution in his maternity hospital in Vienna in 1944, death by puerperal fever (infection of the uterus at childbirth) was common. Despite dramatic reduction in deaths due to hand hygiene it has been a slow process getting physicians to clean their hands between patients. With the increase in multi-drug resistant infections and the increase in use of drugs which suppress the immune system in the treatment of cancer and autoimmune diseases, hand hygiene has become even more important as a way to keep the most difficult organisms to treat from finding new hosts in hospitals. Much research has been done to evaluate the practical and theoretical aspects of various ways to clean our hands.
The big controversy with hand hygiene has been between using alcohol based hand rubs and actual hand washing with soap and water. In the early 2000's various articles came out showing that a gel made of a high concentration of alcohol could successfully kill the majority of pathogenic bacteria without requiring that a person actually find water and wash their hands. This was game changing and resulted in the explosion of new products and the installation of hundreds of thousands of hand sanitizer dispensers in hospitals and other public places. To reap full benefits with these products, the amount of sanitizer must be sufficient to keep the hands wet for 30 seconds. Humans are prone to false economies and so many people will use just a little dab, which is close to useless, and has reduced the practical effectiveness of these things. It also became clear that there were certain organisms which were quite resistant to alcohol, and these were clinically very important. Clostridium difficile, the scourge of the antibiotic treated patient and a common hospital acquired infection is transmitted via spores which are quite alcohol resistant. Hand washing is much more effective for these and chlorhexidine is by far the most effective commonly available soap. In practice, use of hand sanitizer is much inferior to hand washing in nursing home settings in the control of outbreaks of norovirus, also known as the cruise ship virus. This may be because of inadequate use, but norovirus is also known to be resistant to these products. Soap and water handwashing, however, is also prone to failure because people don't spend enough time doing it. Twenty to 30 seconds of handwashing is necessary to remove the majority of microorganisms from the hands, and wiping them with paper towels appears also to be important. Recently non-alcohol based rubs have come out, based on either benzalkonium chloride or benzethonium chloride, which are longer lasting and have a broader spectrum of bacterial killing. These will probably replace the alcohol based products. I am not terribly concerned about the impact on our overall biome with these products since the rest of the skin surface is unaffected and the hands do eventually get recolonized as we touch our arms and faces in normal everyday life. The chemical benzalkonium chloride has been around forever as an antiseptic and so safety is probably not an issue, but I am not totally sure about benzethonium chloride.
While using alcohol based hand sanitizer at a camp with people of various propensities and sensitivities, I was struck by the incredibly strong smell that persisted and so washed my hands after using it. I then realized the totally obvious practical point that it need not be an either/or proposition regarding hand hygiene. When I am not sure which microorganism I am trying to avoid transmitting, I should wash my hands and use hand sanitizer. It just isn't that difficult. With the alcohol based sanitizers, I should use them first, then wash. With the longer lasting chemical rubs, it would probably be best to use them second. In a water limited setting, like in developing countries, alcohol based sanitizers are clearly superior (see this study) to washing with water, even if the hands are visibly soiled, when they are actually available.
The biggest issue in any situation where these things are necessary is instilling discipline: people are just not very good about washing their hands, especially doctor people. It would be easier if they could really see the impact of not doing it, which is often huge. It would also be easier if it was, in fact, easier, and I just ran into a gadget that fits that description at a barbecue shop in Bend, Oregon. A company called Meritech makes a hand washing machine that removes 99+% of bacteria from the hands in 12 seconds using an automatic dispenser of water and an antibacterial soap. It was strange to find one in this restaurant, but the owner told me she just thought it was an excellent idea. It cost her around $5000, and it was really fun to use. It felt like a hand massage and eliminated the issue of re-exposing the hands to bacteria when turning off the faucet. If they put these in hospital rooms, I think they would be a big hit.
But on to water purification. My first trip to Haiti was blessedly without intestinal impact. The next one, though, ended very poorly. I developed a fever, nausea, diarrhea then constipation and liver swelling. I couldn't eat for a month without becoming nauseated. I recovered, at least mostly, but have been very serious about water safety since then. My discomfort clearly sucked, but, more importantly diarrheal disease, mostly caused by water and food contamination, is the second leading cause of death for children under 5 years old and results in the deaths of over 750,000 children every year. It is largely preventable.
The options for eliminating water infection risk are many, and all have pros and cons. Some are new, some are old. I think I know about nearly all of them. To avoid water related disease, we must kill or remove parasites, their eggs, bacteria and viruses. We can use chemicals, filters or radiation to do this. The simplest and oldest effective method of water purification is boiling. If water is boiled for a minute, virtually all microorganisms are killed and it will be safe to drink. Chlorine is toxic to just about every living thing and a little less than a teaspoon of bleach added to 5 gallons of water and left to sit for 30 minutes (the chlorine molecules must reach all of the intended targets) will be safe to drink. The EPA quotes 8 drops of bleach to sanitize 1 gallon of water. If it is left awhile the chlorine gradually evaporates and the taste improves, though it is not bad at all at this level. One must remember that bleach does lose potency over time, and that these proportions apply to fresh bleach, 5-6% sodium hypochlorite. Chlorine dioxide is a more potent bactericide than bleach but is harder to find and more expensive. It comes in both tablets and liquid and leaves virtually no chlorine taste. Aquamira is the product I have used. Povidone iodine, the 10% solution that is used as a medical skin prep, is effective at a concentration of 1:1000, which means 1 ml (15 drops) in a liter of water, when left for 15 minutes. It also doesn't taste too bad, but will turn purple if mixed with starch, so is quite alarming if used to cook pasta. Tincture of iodine and iodine tablets are more potent but a little harder to come by.
Ceramic filters, like those used for backpacking, remove all but the smallest viruses. Unfortunately hepatitis A and E, which cause lots of bad disease in developing countries, are not removed by ceramic filters and can be present and infectious in water. These filters, like the Katadyn pocket water microfilter and the MSR Sweetwater, are very compact and can be used to remove bacteria and protozoa from huge quantities of stream water, as well as removing undesirables like pine needles and algae and grit. They are absolutely fine for most uses but are not adequate, alone, for places where virus contamination is an issue.
A few years ago a British engineer came up with a super fine filter that eliminates viruses as well and is very simple to use. The name of the company is Lifesaver and it has been marketed to the military and well as being introduced into water limited settings where people drink from puddles with obvious contamination. I got one of these because I was impressed with the demonstration video and could see how it would potentially save lives. They make 750ml bottles, which I bought, and big multiple gallon jugs which can be filled from any water source, even really nasty ones, and then a low pressure pump pushes the water into a reservoir from which it can be used. The contraption is heavy, about a pound and a half, but tough and easy to use. I used it exclusively in Tanzania and was blissfully without intestinal ills. It costs nearly $200 and is rated to be able to purify 6000 liters before the filter needs to be replaced. They recommend replacement of the charcoal filter after each expedition, but that is not required for safety.
The most surprising technology to me is ultraviolet (UV) light treatment. UV light has been used for water purification for decades, but recently small pocket lamps have become commercially available which can be used on the fly. Ultraviolet light attacks DNA and RNA, the genetic materials of cells, and kills everything whose function depends on these, which is basically everything. The UV radiation in these devices is very high frequency and depends on the water being nearly completely clear to work. It cannot penetrate particles of poo floating in water. It is an excellent way to treat water from the tap or water that has been filtered or is visibly without particles. UV light is increasingly used to treat city water sources since it doesn't depend on toxic chemicals to work. It does, however, depend on electricity. I bought a steripen, which is a device about the size of an electric toothbrush, which recharges from a USB port. I also have a solar battery which a USB output so I am set, but some of the pens require rechargable AA batteries which are a little less flexible in resource poor settings. With the pen, you simply press a button on the handle and stir the water in a liter bottle for 90 seconds until the pen indicates the process is complete. Camelback makes a bottle with the UV source built in, also with a rechargeable battery with a USB connection. These contraptions all cost around $100. It is also possible to purify water by placing it in a PET plastic container in full sunlight on a roof for 6 hours, using both the heat and the UV to kill anything living in it.
I'm headed to Haiti and South Sudan in the next two months and will bring my Lifesaver bottle and Steripen, with some povidone 10% for backup. I will eat cooked food or fresh fruit that I can peel. I absolutely promise not to drink the delicious glasses of whatever they offer me even if I know they will taste amazing and I am very thirsty. Except tea if I see the water boil. That is really the hardest thing. Not eating cabbage salad. Not drinking the glasses of yummy juice punch. I will remember what it was like to be nauseated for a month with a swollen liver. I will use hand sanitizer and then wash my hands, whenever there is water available to do so. In Haiti we will again work on projects to improve waste disposal and promote water purification (bleach treatment is probably the most practical there). My resolve is firm, my research extensive and my experience instructive.