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.)

Dear Doctor: Everybody’s suddenly talking about how it’s important to eat some walnuts every day. Who decided that? Why is there always a new food fad?

Dear Reader: It’s a challenge to keep up with the latest superfood that’s going to change your life. Blueberries, broccoli, chia seeds, kale, acai berries, pea flour, fish oil, oatmeal -- and the list goes on -- have all had their day. Health promises include fast and easy weight loss, lower blood pressure, better cholesterol levels, improved mood and even disease prevention.

This wish for a cure-all is as old as time, with a diabetes remedy of okra and wheat germ dating back to ancient Egypt in 1550 B.C. Thousands of years later, we still love the notion of a food with special properties that extend beyond its nutritional profile. It’s that ongoing wish for a magic bullet that fills our newscasts and headlines with an ever-changing list of miracle foods.

As you point out in your letter, one of the newest entries into the superfood pantheon is the walnut. The reason why is recent research that links walnuts to certain health benefits. A study from scientists at Penn State found that people who ate several ounces of walnuts each day saw an increase in the populations of several types of gut bacteria. Among these were gut bacteria associated with blood pressure regulation and with improved heart health. This echoes the findings of previous studies, which have linked a diet that includes walnuts with a reduced risk of heart disease. The subjects in the Penn State study also saw an increase in the numbers of a gut bacterium that may help to protect the lining of the gut. This holds promise for conditions such as leaky gut syndrome and inflammatory bowel disease.

The results of another study, conducted by researchers at Loma Linda University Adventist Health Sciences Center, was published earlier this year in the American Journal of Clinical Nutrition. Those findings suggested that eating walnuts may have a beneficial effect on cognitive decline in older adults who have existing risk factors for the condition. Similar effects on cognitive function were not seen in healthy older adults.

Both of these are small studies. The Penn State research included 42 volunteers. The Loma Linda University study looked at data from 640 “free-living” older adults in California and Spain. In addition, the authors of the Loma Linda University study disclosed that it was completed with funding from the California Walnut Commission.

We’re not complete skeptics when it comes to superfoods. The truth is that many are indeed rich in an array of vitamins, minerals, fiber or micronutrients associated with improved health and well-being. But rather than concentrate on a few unique and important foods, we like to think in terms of what some licensed nutritionists are now calling the “super plate.” That is, a healthful and balanced diet made up of whole, fresh foods from a wide variety of sources. You’ll feel better, you won’t get bored and your body will thank you.

(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.)