Dear Doctor: I'm familiar with hepatitis C's connection to death, but hepatitis A? I had no idea that could be lethal, and now I'm reading about a number of deaths in San Diego. I thought anyone could get hepatitis A.

Dear Reader: You're right, anyone can get hepatitis A. That's what makes the current outbreak alarming, but only if you don't know how, or are unable, to protect yourself. First, some background: Hepatitis A occurs in about 1.4 million people worldwide each year; in the United States, only about 1,200 to 2,500 people are infected per year, primarily in sporadic outbreaks.

The virus is released in the stool of infected people, and from there it can move to their hands. It's resistant to detergents, high temperature and solvents. Frequent handwashing can reduce the risk of transmission, but some of the virus can linger. A significant factor in hepatitis A transmission is that a person can transfer the virus to others even before he or she shows symptoms. In areas of poor sanitation, hepatitis A can easily be transferred among the population. This is why the disease is so prevalent in developing countries. Hepatitis A also can be transferred via contaminated foods, like shellfish, that have come in contact with the virus.

San Diego's hepatitis A outbreak is blamed on poor sanitary conditions, with related contamination of food sources. This has led to more than 400 cases since November 2016; 16 have been fatal. Many of these cases have occurred in the homeless population, which lacks proper sanitation facilities, leading the city to clean many of the streets with bleach and to provide portable handwashing stations in areas frequented by the homeless.

Once ingested, the hepatitis A virus moves into the bloodstream and then into the liver. There, it replicates in the liver, causing the immune system to attack the infected cells. This, in turn, leads to massive liver inflammation. Shortly after infection, patients experience nausea, fever, fatigue, poor appetite and stomach pain. A few days later, 40 to 70 percent of patients will have a yellowish discoloration of the skin and severe itching. For the majority, this is as bad as it gets, and symptoms improve after two weeks. In fact, 85 percent of patients will have full recovery within two to three months, and nearly 100 percent have full recovery at six months.

In contrast, hepatitis C and sometimes hepatitis B cause a chronic low-grade infection that can lead to cirrhosis of the liver and liver cancer. For people who already have chronic hepatitis C or B, hepatitis A can more readily lead to liver failure and death. Also, people over the age of 50 have greater difficulty recovering from hepatitis A, leading to dehydration, other infections and death.

In short, good public sanitation, handwashing and vaccination for hepatitis A can prevent infection. Children now routinely get vaccinated for hepatitis A, which has decreased the incidence of hepatitis A not only in children, but also in the general population. People with chronic hepatitis B or C should also be vaccinated against hepatitis A to reduce their risk of death should they become infected, as should homosexual men and IV drug users.

So, while hepatitis A is rare in the United States, incidents such as the one in San Diego highlight the need to be vigilant against the disease.

(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: I graduated from college last spring, and I just got my first full-time job, which I love. But it means that I'm sitting for more than eight or nine hours a day, and I hate it. Would one of those treadmill desks be a good way to stay fit?

Dear Reader: Congratulations on your new job! The transition from the free-form life of college to the structured schedule of full-time work can be bumpy. We think it's great that you're looking for a creative way to mitigate this particular challenge in your new work routine.

Research has repeatedly shown that sitting for long periods of time is bad for your health. Your heart rate drops, circulation slows and muscles quickly lose their tone. Many of us tend to lean or slump, which puts necks, shoulders and spines at risk of injury. Add in the fact that all those hours spent in a chair each day have been linked to high blood pressure, elevated cholesterol levels and a decline in insulin response, and long-term sitting is risky business.

A study published in the American Journal of Preventive Medicine last year ups the ante. Researchers analyzed data collected in 54 different countries regarding people who remained seated for three or more hours per day. They found a link between how long someone stays seated each day and an increased risk of premature death.

Although additional exercise didn't diminish that increased risk, replacing the time spent sitting with either standing or walking did. Which is where your question comes in about the growing trend in the treadmill desk -- that's an elevated desk with a treadmill in place of a chair.

The short answer is that yes, a treadmill desk can be a very good solution to too much sitting. Rather than spending your time immobile as you read, type or talk on the phone, you're moving at a steady, gentle pace. Walking not only can lower the risk of high blood pressure, heart disease and diabetes, it can also strengthen muscles and bones, and may help you stay in a healthy weight range.

But there are caveats. First of all, the components of the treadmill desk have to be strong, stable and ergonomic, or you risk injury. You can't just throw a thrift shop treadmill under an elevated platform and go. Secondly, it takes practice -- certainly weeks and maybe even a month or two -- to learn to walk and work at the same time. Productivity drops at first, as does concentration. But according to the National Institutes of Health, over the long term, the gain in well-being is worth it.

If a treadmill desk isn't something your new employer is willing to invest in, you can still incorporate specific behaviors to counteract the damage done by prolonged sitting. Get up every 15 minutes or so to stretch and take a quick walk. When you sit back down, reset your posture. Take your phone calls standing up. Instead of emailing, walk over to your colleague to speak in person.

We wish you good luck in your new job. And if you do get a treadmill desk, please let us know how it goes.

(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: A recent study suggested that cancer for thyroid treatment can be delayed. What would be the point?

Dear Reader: The question is a logical one -- as I know firsthand, having been diagnosed with papillary thyroid cancer about 20 years ago. At that time, the only thought that my family and I had was: How quickly can we get this cancer out? I have had no recurrence and have not regretted my decision. But now cancer patients have the advantage of data.

Thyroid cancer rates have increased over the last 40 years. In 1975, the rate of papillary thyroid cancer -- the most common form of thyroid cancer -- was 4.8 per 100,000 people in the United States; in 2012, the rate was 14.9 per 100,000 people. While the increase in diagnosis is partly due to exposure to radiation from cancer therapy, X-rays and nuclear waste, it's mostly due to detection. Thyroid cancers are simply found more often today, often incidentally when imaging of the neck or chest, done for other reasons, shows a mass in the thyroid.

Such cancers are not uncommon. In U.S. and other countries' autopsy studies of people who have died for other reasons, researchers have found that 5.7 percent to 13 percent of people have small papillary thyroid cancers. That suggests that people with these cancers may never develop negative effects from them.

That brings us to the 2017 study that followed 291 patients with papillary thyroid cancers of less than 1.5 centimeters. Instead of having surgery on their thyroid, they received ultrasounds every six months for two years and then yearly afterward. On average, patients were followed for 25 months and received four follow-up ultrasounds. Only 11 (3.8 percent) of the 291 patients saw their tumors grow more than 3 millimeters during the study period. However, tumor volume increased by 50 percent in 36 patients (12.1 percent) and decreased in volume by 50 percent in 19 patients (6.5 percent). Those younger than 50 had a five-times-greater likelihood of tumor growth than people older than 50. Japanese studies have found similar results.

Traditionally, for thyroid cancers less than 1 centimeter, treatment involves removal of one of the two lobes of the thyroid. For cancers greater than 1 centimeter, the entire thyroid is removed. Because such surgery requires a patient to take thyroid hormone for the rest of his or life, it's better to avoid surgery if possible. So, here's what does the data tell us:

In essence, older patients with small papillary thyroid cancers can postpone a decision on surgery and rely on twice-a-year ultrasounds of the thyroid, at least for a while. That means, if you're a 70-year-old with a papillary thyroid cancer of 1 centimeter, simply monitoring the cancer could help you avoid unnecessary surgery. However, if you're 70 years old with a 2-centimeter lesion, then surgery to remove the thyroid is appropriate.

The same does not always hold true for younger patients. If you're a 35-year-old with a 1.2-centimeter papillary thyroid cancer, postponing surgery can be risky due to the higher likelihood that the cancer will increase in size.

Regardless, with the rates of thyroid cancer increasing in our population, it is important to continue studies on the most appropriate treatment.

(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.)