Hello, dear readers, and welcome back to our monthly letters column. We’re happy to report that you’ve kept our mailboxes full, so we’ll dive right in.

-- Pet-related topics always get a lot of mail, and a recent column about a study into the health benefits of living with a dog was no different. A reader from Tulsa, Oklahoma, wrote to say that limited mobility need not be a barrier to canine companionship. “People who are physically unable to walk a dog outdoors can experience the joy provided by a pet and the other benefits of pet ownership, particularly with a small breed,” she wrote. “They can be trained to use potty pads indoors. We recently adopted a 3-year-old rescue Chihuahua who quickly learned to use the potty pads. As I write this, my current ‘favorite child’ is right here beside me. Life is just better with a pet in your lap.”

-- A reader from Coeur d’Alene, Idaho, who volunteers at a local hospital with her therapy dog, wrote to say she sees the happiness that a dog imparts with every visit. “It’s refreshing to read about how dogs make a difference in the healing process. I witness that emotion every time we visit,” she wrote. “And, as you pointed out, the nurses, doctors and support staff all love interacting with the dogs as well."

-- In response to a column about carpal tunnel syndrome, a reader from Fresno, California, found that a small tweak to his work habits made a big difference to the severe carpal tunnel pain he experienced while using a mouse during computer work. “I went to several doctors, but ultimately decided to just move the mouse to the left side of the keyboard,” he wrote. “It was awkward for about a week, but eventually I adapted, and after two months, the pain was gone.” Since then, he switches hands on the first day of each month and reports, “my carpal tunnel pain has never returned.”

-- A column about the flu that mentioned that symptoms can be similar to those of a bad cold left a reader in Spokane, Washington, confused. “All my life -- 62 years -- the flu has been referred to as an illness with symptoms such as fever, stomach upset or vomiting, lack of appetite, diarrhea and achiness, and it seems to take longer to get well from than a cold,” he wrote. “Have I been confused about what flu really is?” To clarify, the flu is an infection of the influenza virus. It typically shares respiratory symptoms with the common cold, and can cause the additional symptoms that you mention. The diagnostic difference between the flu and a cold is the virus that causes each infection. And, as you mention, the flu lasts longer than a cold and tends to be more severe.

That’s it for this month. Thank you again for all of your questions, tips, comments and kind words. We love hearing from you. And just a reminder to new readers -- we can’t make a diagnosis, recommend medications or offer a second opinion.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Would you please explain the terms we keep hearing in news reports about that new virus, like “epidemic” and “outbreak” and “pandemic”? It seems like they’re being used interchangeably, and it makes it hard to understand what’s really going on.

Dear Reader: You are referring to what initially was known as Wuhan coronavirus, a new respiratory illness identified in China at the end of December 2019. The name referred to the city where the illness first appeared and the specific virus that causes it. In mid-February, the World Health Organization officially gave the virus a name -- COVID-19. That breaks down to “CO” for corona, “VI” for virus, “D” for disease, and 19, which indicates the year this new illness appeared.

Your question is important because each of the terms you mention -- outbreak, epidemic and pandemic -- refers to a different type of event. They arise from a branch of medicine known as epidemiology, which is the study of how, where and why disease and illness spread, and how to predict and prevent them. And we agree that misusing these terms can lead to confusion and misunderstanding.

An outbreak is a disease or condition that occurs in greater-than-expected numbers. The departure from the norm can include the time of year during which the increase in illness appears, the specific group of people it affects, the geographical area it covers or the type of illness itself. For example, polio has become so rare in the U.S. that just a handful of cases in one area would be considered an outbreak. At the other end of the spectrum is the influenza virus. We have become so accustomed to the annual surge in influenza infections that, rather than calling it an outbreak, it is often referred to simply as “flu season.”

An outbreak that increases rapidly in both the number of new cases and in geographic scope is referred to as an epidemic. That’s what happened with COVID-19, which began as a localized outbreak in Wuhan and then spread throughout much of China. In this case, the epidemic was caused by a new strain of coronavirus that health officials believe “jumped” from animals to humans.

When an epidemic spreads across the globe, it’s known as a pandemic. The numbers of people who become ill, as well as the fatality rate, is much higher in a pandemic. Unfortunately, some news reports are misusing the word when talking about COVID-19. While it’s true that the virus has spread to other nations, the numbers of cases outside of China remain quite low at this time and don’t meet the definition of a pandemic.

A lot of people in the United States are worried about the new coronavirus, but the risk here is low. We agree with health officials who say that the greater health risk continues to come from our own ongoing influenza season. Respiratory viruses enter our bodies via the mucous membranes in the mouth, nose and eyes. So wash your hands often, don’t touch your face, and seek treatment and stay home if you’re sick. And remember, it’s still not too late for a flu shot.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I’m 66 years old, and I seem to be of an age at which the people I know are being diagnosed with COPD. I’ve heard it mentioned in TV ads, but I still don’t really understand what it is. Who gets COPD? Is there a cure?

Dear Reader: Chronic obstructive pulmonary disease, commonly referred to as COPD, is the name for a group of lung diseases in which it becomes difficult to breathe. It is caused by lung damage and chronic lung inflammation, which produce symptoms that include wheezing, persistent coughing, an excess of mucus in the lungs, a sensation of tightness in the chest and shortness of breath, particularly during and after physical exertion.

Because COPD diminishes lung function, the amount of oxygen that is available to the body is reduced. This leads to symptoms like weakness and fatigue, and it can even cause the lips or fingernails to take on a blueish color.

The two most common types of COPD are emphysema and chronic bronchitis. In emphysema, the tissues in the smaller airways and air sacs in the lungs become damaged, which makes breathing increasingly difficult. Chronic bronchitis results in the over-production of mucus in the airways due to inflammation. This causes a persistent cough as the lungs attempt to clear the mucus. It also leaves the individual at increased risk for repeated respiratory infections. The disease is caused by long-term exposure to fine particulates and other irritants that damage the airways and the lungs.

The leading cause of COPD is a history of smoking cigarettes. It can also be caused by environmental exposure, such as air pollution and second-hand smoke, or industrial exposure, such as in coal mining, tunnel work and certain manufacturing and chemical processes. People with a deficiency of alpha-1 antitrypsin, a protein that protects the lungs, also can develop COPD despite having no other risk factors.

To diagnose COPD, your doctor begins with a detailed medical history to assess exposure to pollutants, including cigarettes. Lung function tests are used to measure the amount of air someone can inhale and exhale and whether or not adequate amounts of oxygen are being delivered to the blood. The most common of these is spirometry, in which the person blows through a tube and into a gauge called a spirometer. The spirometer measures two markers of lung function -- the volume of air the lungs can hold and how efficient they are at expelling that air.

Scans such as a chest X-ray or CT scan may be used to detect emphysema, and to rule out cancer or heart failure. A blood test known as an arterial blood gas analysis reveals how efficient the lungs are at delivering oxygen to the blood and removing carbon dioxide, a waste product.

Treatment includes medications known as bronchodilators, which relax and open the airways to make breathing easier. In more severe cases, oxygen therapy and inhaled steroids to reduce inflammation may be recommended.

Lifestyle changes are just as important. These include quitting smoking. Staying active is important, and your doctor can help craft an appropriate exercise plan. Remember, COPD is a progressive disease, and patients who receive consistent medical care have the best outcomes.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)