Dear Doctor: Proton pump inhibitors, which I take for my severe heartburn, have made my life enjoyable again. Now I'm reading that they may cause kidney damage. How serious is the risk? I really don't want to give them up.

Dear Reader: Severe heartburn, which is the burning sensation behind your breastbone that comes on after a meal, can be debilitating. Caused by the presence of stomach acid, it's an irritation of the lining of the esophagus, the muscular tube that runs between the throat and the stomach.

When things are working properly, a ring of muscle fibers in the lower esophagus prevents the contents of the stomach, including the powerful acids that break down food, from moving back up and damaging tender tissues. This ring of muscles is known as the lower esophageal sphincter, or LES. However, in some people, the closure of the LES is incomplete. This allows the stomach acids to back up into and potentially damage the lining of the esophagus, which is known as reflux.

Proton pump inhibitors, or PPIs, are extremely effective in alleviating chronic and severe heartburn. They reduce stomach acid by blocking the action of an enzyme in the wall of the stomach. But numerous studies have raised serious questions about a potential link between PPIs and kidney disease.

A pair of studies published in 2016 in the Journal of the American Society of Nephrology and JAMA Internal Medicine looked at information collected from tens of thousands of patients in two separate databases. The results backed up the previous research -- that patients taking PPIs were at higher risk of developing kidney disease than individuals who used a different class of drugs, known as H2 blockers, to address the same digestive issues.

In the two 2016 studies, it was found that the risk of developing kidney disease was increased among patients who took PPIs twice daily. Additionally, that risk rose over the first two years of PPI use, according to the results of the studies. The studies addressed only prescription drugs and not over-the-counter PPIs. This is because the data relating to non-prescription PPIs are not readily available.

Although some experts in the field of nephrology now believe these drugs may cause harm in some cases, others suggest that the studies, which are observational rather than clinical, have significant limitations. Additionally, the data pool includes many individuals who are already in poor health. Experts who are taking a more cautious approach suggest this makes a direct connection between PPIs and kidney damage more difficult to prove.

As to your own situation, we think it's important that you make an appointment with your family physician to talk things over. First of all, it's possible that there may be non-medical alternatives to managing your chronic heartburn. Losing weight, eating smaller meals and changing your diet can be surprisingly effective. If it turns out that your physician feels you do require medication, discuss the option of using H2 blockers, medications which also reduce stomach acid. While not quite as effective as PPIs, switching away from PPIs may give you peace of mind.

(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: Amid all the talk about the Zika virus, I thought we'd stopped worrying about West Nile. Now I see that it's back -- or never left. What are the risks of this? Are they greater than Zika?

Dear Reader: You are correct; West Nile virus continues to be a threat in the United States. Forty-eight states and the District of Columbia have reported cases of West Nile; overall, the U.S. reported 43,937 cases of the virus and 1,911 related deaths between 1999 and 2015. Because many people have only mild symptoms and don't seek medical attention, the actual number of cases is undoubtedly much higher.

The species of West Nile virus in the U.S., which was first detected in New York City in 1999, is believed to have originated in the Middle East. It's transmitted by mosquitos, which starts the disease cycle by infecting birds. There, the virus multiplies within its avian hosts. When another mosquito draws blood from an infected bird, the mosquito then can infect another bird, or a human. Because transmission relies on mosquitos, most cases of West Nile virus occur in the summer and early fall months, when the insects are most plentiful. Humans rarely transfer the virus among themselves; when they do, it's because infected mothers pass the virus to their child in the womb.

The majority of people with West Nile virus infection don't have symptoms; in fact, symptoms are seen in only 20 to 40 percent of cases. Further, early symptoms (fever, muscle aches, headache, fatigue and rash) are not much different from those of many other viruses, so the true cause may go undiagnosed. These symptoms usually last from three to 10 days, but some people report fatigue, muscle aches and difficulty concentrating for up to 30 days or longer after contracting West Nile virus.

In less than 1 percent of people, West Nile virus invades the nervous system. There it can cause inflammation of the brain and surrounding tissues, leading to confusion and even coma or death. The virus can also enter the peripheral nerves, causing muscle paralysis; sometimes, this paralysis involves the respiratory muscles, leaving some people unable to breathe on their own. The death rate when West Nile virus invades the nervous system is 10 percent. Those at higher risk of death from West Nile virus include older adults; people with diabetes, heart disease or chronic hepatitis C; people with a depressed immune system; and people who abuse alcohol.

Patients who survive West Nile virus' assault on the nervous system can have prolonged symptoms. One-third of those with paralysis related to the virus will fail to improve, and if the brain is affected, people can experience significant difficulties with brain function even after a year. One study found that 40 percent of patients reported fatigue and weakness up to eight years after the infection.

As for treatment, anti-viral medications appear to have some effect against West Nile, especially when the drugs are used early in the disease. However, no large human studies have assessed their efficacy. The best way to avoid West Nile virus is by draining areas of standing water or using mosquito repellants.

While other viruses, such as Zika, are understandably worrisome, don't ignore the possibility of infection with West Nile. In the continental United States, Zika transmission is much rarer than West Nile transmission.

(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: Thank you for your column about service dogs and the tasks they perform. I wonder whether you could go a step further and explain the best way for people to respond when they see a working dog? A colleague of mine is blind, and dealing with well-meaning people who want to pet his dog adds another level of difficulty to his daily life.

Dear Reader: For many of us who are animal lovers, it can be tempting to initiate an interaction with either a service dog or its owner when we see them together out in public. The dogs are so devoted and well-trained that it's natural to want to praise or pat them, and perhaps to learn more about them and their owner.

However, there are distinct rules of etiquette that, when observed by the rest of us, make life easier for the handler and the dog when they are out in public. Part of this is safety, and part of this is privacy. The presence of a service animal signals a special need, which does not give strangers permission to breach the anonymity we all expect and deserve when we are out in public. And it's important to remember that even when they appear to be just standing, sitting or even napping, these dogs are at work.

Never interact with a service dog. These animals are trained to ignore you so that they can stay fully focused on their handler and the tasks at hand. That means you shouldn't try to catch the dog's gaze; pet it; give it a treat or a toy; call to it; or even speak to it.

The dog and its handler are a team, mentally and physically in sync. When you disrupt the dog's concentration, you can cause it to miss a vital cue when its owner needs help. By ignoring the dog completely, you are not being rude. In fact, you are showing good manners.

Quite often the service dog will accompany someone without a visible disability. It's natural to have our curiosity piqued, to wonder what kind of help the dog provides, but the truth is that it's none of our business. Just as you wouldn't quiz the people in line with you at the pharmacy about what drugs they are getting and why, you shouldn't ask the service dog handler any personal questions. Health issues are a private matter.

If you are out with your own pets and encounter a service dog, the same rules apply. Don't let your dog approach, sniff, bark at or try to play with the working dog. Although service dog training includes ignoring other animals, allowing your pet to try to interact with a service dog makes that dog's working day more difficult.

If you absolutely must pet the service dog, always ask the handler first. Don't be surprised or insulted if the person declines, though. Just like you, these folks have errands and tasks to do and want to go about their day.

A good compromise is to simply tell the handler, "What a beautiful dog," and leave it at that.

(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.)