Dear Doctor: My daughter has been talking about the merits of "raw water" -- and the perils of regular tap water. Could it be that people are really drinking non-sterilized or treated water? Isn't that dangerous?

Dear Reader: Thanks to a recent feature story in The New York Times about several companies in the United States that are selling so-called raw water, there's now a national conversation about this trend. The water referred to in the story is untreated, unfiltered and unsterilized. The purveyors claim it is bottled in the exact state that it emerges from certain springs, and attach all sorts of health claims to their products.

While these companies say that the water they sell is safe for consumption (it turns out that one of these vendors, who charges upward of $20 per gallon, is actually drawing from the very same aquifer that furnishes part of Oregon with tap water at a fraction of the cost), the idea that people would seek out so-called natural water is alarming.

The truth is that securing clean drinking water has been one of the great challenges throughout history. Untreated water can contain everything from parasites, viruses and bacteria to naturally occurring chemicals like arsenic. And while municipal drinking water certainly has its own share of black eyes, as the scandal in Flint, Michigan, has most recently illustrated, the idea that spring water is automatically safe to drink is naive and dangerous.

According to the Environmental Protection Agency and the Centers for Disease Control and Prevention, drinking untreated water puts you at risk for any number of pathogens such as E. coli, hepatitis A, Shigella, giardia and norovirus, to name just a few. Diarrhea, cholera, dysentery, typhoid and polio are all water-borne illnesses. Add in wild card pollutants like pesticides, farm waste runoff, carcinogenic compounds and leakage or even spillage from septic tanks -- all of which can leach into the ground miles upstream of a seemingly pristine spring -- and drinking "raw" water can become a genuine health risk.

Clean water is an international health issue. In developing nations, water contaminated with pathogens and pollutants accounts for 80 percent of all disease. According to the World Health Organization, more than 300,000 children under the age of 5 die each year from gastrointestinal illness associated with the lack of potable water. As any experienced backpacker will attest, drinking unfiltered, untreated or unsterilized water is a foolhardy gamble that can result in grave health consequences.

This isn't to say that public water supplies are perfect. According to a report issued by scientists with the National Resources Defense Council last year, the aging municipal infrastructure in the U.S. is taking a toll on water safety. Violations of the landmark Safe Drinking Water Act of 1974 range from inadequate testing and reporting to the presence of a host of contaminants in community water systems.

Still, in our opinion the so-called raw water movement is misguided. While some natural sources may indeed be perfectly safe, the health risks of drinking untested water from a spring or pond far outweigh the chances you take at your kitchen faucet.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Would you kindly address the risks of e-cigarettes compared to regular cigarettes? I am opposed to both because of the potential for nicotine addiction and other health issues. Some of my adult relatives, however, are convinced e-cigs are not harmful, even though they clearly seem addicted.

Dear Reader: On the surface, e-cigarettes appear to be a good idea. After all, they contain no combustible substances to become residue and enter the lungs. Instead, the devices feature a cartridge filled with a nicotine liquid that is vaporized and inhaled. Nicotine concentrations vary in the cartridges from 6 to 24 milligrams per milliliter. E-cigarettes also contain propylene glycol, which is used to prevent the liquid from evaporating, and flavorings that make the vapor more palatable.

As for their safety, first, let's assess the risk from nicotine. It's true that nicotine raises the pulse rate and increases the workload of the heart, but while smoking cigarettes is a significant risk factor for coronary artery disease and heart attacks, nicotine does not appear to be the culprit. In fact, studies have shown that people who use nicotine replacements in the form of gum, lozenges or patches have no change in their risk of heart attacks. Note, however, that rates of nicotine toxicity have substantially increased since the introduction of e-cigarettes. This occurs when someone uses too much nicotine or when someone, such as a child, ingests the liquid in one of the vials.

Second, let's assess what we don't know: the long-term effects of inhaling e-cig vapor. Acute exposure to the vapor does lead to a small increase in lung flow resistance, and the vapor could lead to more inflammation of the airways. Surveys of students in Hong Kong and in the United States have shown an increased rate of chronic cough and bronchitis among those using e-cigarettes. The vapor itself does have trace amounts of carcinogenic compounds, but at much lower levels than in combustible cigarettes.

Because the risk for lung cancer would appear to be smaller for e-cigs than for traditional cigarettes, they definitely have the edge in that respect. Additionally, e-cigarettes, like nicotine gums and patches, can decrease the desire to smoke combustible cigarettes. Studies of people using e-cigarettes to stop smoking have found rates of smoking cessation of 7.3 to 12.5 percent. And even if e-cigarettes don't actually help people stop smoking, they could theoretically decrease the number of regular cigarettes consumed. So, for those who smoke cigarettes already, e-cigarettes could provide a health benefit.

The bigger problem lies in e-cigarettes' risk to young people. Studies have shown that adolescents and young adults who use e-cigs have three times the risk of initiating regular cigarette smoking than those who don't use e-cigs. This may be due to the nicotine, of course, but regardless, it points to the potential connection between e-cigs and a lifelong nicotine addiction, with e-cigs being a gateway. Because of this potential, many doctors and anti-smoking activists have advocated banning advertisements geared toward adolescents.

In summary, perhaps the harm to your adult relatives depends on their smoking status and age. In any case, allow me to reiterate: While e-cigs seem healthier than traditional cigarettes, the long-term health effects are not known.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Readers: With this year's flu season on a pace to be the worst in almost a decade, we want to take a moment to share an important letter that we received from a reader. As of this writing, at least 37 children have died from influenza infection. Because of the time lag in identifying and reporting flu deaths, officials suspect the true number is significantly higher.

Medical centers throughout the United States have admitted close to 12,000 people with confirmed cases of the flu, in many instances overwhelming the facilities. Here in California, some hospitals have resorted to setting up "surge tents" to house the crush of flu patients. Nurses and other medical personnel are being flown in from surrounding areas to help. And the capper is that, driven by H3N2, a particularly nasty strain of the influenza A virus, scientists at the Centers for Disease Control and Prevention warn that things will probably get worse.

Which brings us to the letter -- it's a plea, really -- from one of our readers. She begins by sharing that, in the five years after her diagnosis of rheumatoid arthritis, she has managed to find a treatment regimen that helps her live with this difficult disease. However, this includes medications that make her particularly vulnerable to infection. We'll let her take it from here:

"The same medications that keep my disease under control also suppress my immune system and leave me vulnerable to catching colds and other viruses that my body is unable to fight off," she writes. "As a result, I am very careful about being around other people in public places or in crowds. My request is that you please let others know that if you are not feeling well or are sick to please stay home! Those with compromised immune systems cannot fight off illness the way that you can. This has been a bad year for the flu, but it can be deadly to someone like me."

Research shows you're capable of spreading the influenza virus a day or so before you realize that you're sick. You'll continue to be capable of spreading the virus for another five to seven days. For children, it can be even longer. So the minute you recognize the onset of your own flu symptoms, whether it is fever, chest congestion or body aches, know that you're contagious. Always cover your mouth when you cough. Sneeze into a tissue. Wash your hands. Stay at home.

We have long understood that flu is transmitted via the fine mist of aerosolized droplets from a sick person's cough or sneeze. Now a new study, funded by the CDC, suggests the virus is passed along on an infected person's breath, whether or not they cough or sneeze. People are particularly infectious early in their illness, yet another argument for staying home.

The advice for staying healthy has long been frequent hand-washing, keeping surfaces clean and steering clear of individuals who are ill. While this all still holds true, researchers in the study say staying away from enclosed public spaces is equally important.

And, we would add, get your flu shot. This year's version isn't as robust as one would have wished, but it does offer a measure of protection.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)