Dear Doctors: My wife started getting sick a few days before Halloween. We were worried that it was going to turn into a bad respiratory illness, but it stayed in her nose and throat. That's a common cold, right? Why is having a cold so different from when you get the flu?

Dear Reader: Both of the illnesses you mention in your letter -- the flu and a cold -- fall into the broad category of upper respiratory infections. Because different types of viruses cause each one, the body's response can vary a lot. The flu can cause serious illness and can lead to hospitalization and even death. The common cold, by comparison, is shorter in duration, with symptoms that are not as bad. Having a cold isn't fun by any means, but it's not a serious threat to health. To understand why, we need to take a closer look at the microbes involved.

Influenza, commonly known as the flu, is caused by specific subtypes of the influenza virus. Most often this is influenza A and influenza B. The flu hits hard and fast due to the nature of the influenza virus. People shed the influenza virus through droplets primarily spread by coughing or sneezing. When others inhale the flu virus, it absorbs through their mucous membranes. Then the flu virus penetrates deep into the tissues that line the airways. The virus can evade early immune detection by shielding itself from the sentinel cells of the immune system. By the time the immune system finds this invader, the viral infection has grown, so the body triggers a powerful inflammatory response to fight it.

The common cold, by contrast, is a milder infection. Symptoms usually start gradually over a day or two. Colds are most often caused by rhinoviruses. These viruses tend to stay in the upper airways and trigger fewer and less intense immune responses. The immune system also recognizes the infection earlier, so the body has a slower and more measured inflammatory response.

An interesting fact: There are several types of rhinovirus that can cause the common cold. That’s why it’s possible to have two colds in a row. You aren’t catching the same cold twice, but responding to two separate rhinoviruses.

Medical care for a cold and the flu also differ. Treatment for a cold focuses on managing your symptoms. Usually, over-the-counter meds help ease pain and relieve sinus and nasal congestion. Getting plenty of rest helps, as does drinking lots of fluids to replace what the body uses to produce mucus. For a mild case of the flu, a similar treatment, along with cough medicine, can be enough. But for serious flu symptoms, you want to check with your doctor. They may recommend a prescription of antiviral medications. Starting these medications in the first two days of an influenza infection can shorten the illness. If someone with the flu has worsening symptoms, including chest pain or high fever, they should seek immediate medical care.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Kansas City, MO 64106; 816-581-7500

Dear Doctors: I am a 74-year-old female and was diagnosed with popliteal artery stenosis in my left calf. When walking briskly, it is bothersome to painful. I stop, stretch and can continue, up to 4 miles most days. My internist has suggested I start taking Wegovy. Is this a known treatment?

Dear Reader: Let’s begin with defining your diagnosis. Popliteal artery stenosis is a form of peripheral artery disease, or PAD. This is a fairly common condition. The arteries in the legs, arms or pelvic area get narrower. This reduces blood flow to the area. (The medical term “stenosis” means narrowing.) Risk factors for PAD include high blood pressure, poor blood lipid profiles, diabetes, being overweight or obese and smoking. Family history of cardiovascular disease is also a factor, and older adults have higher risk of PAD.

The popliteal artery reaches from the lower thigh to the upper calf. It lies just beneath the two heads of the gastrocnemius, the large calf muscle, as it passes behind the knee. Popliteal artery stenosis restricts blood flow to this large muscle. The muscle doesn’t get enough oxygen or nutrients, which allows waste products to build up. This can lead to the pain and cramping that you describe. When you pause to rub your calf, you are giving the tissues in the calf time to recover from the lack of oxygen caused by the stenosis. This is why your symptoms improve after a break.

With the recommendation of using Wegovy, a semaglutide medication, your doctor is following new data on reducing cardiovascular risk. New research has found that these medications can improve the metabolic health factors that contribute to atherosclerosis, and thus PAD. A recent study looked at 792 people living with diabetes who also had peripheral artery disease. The participants who used a semaglutide medication reported a marked decrease in PAD symptoms. They were also able to walk for longer distances. A different study that followed 1,363 people with PAD over the course of almost four years had similar results.

While these results are encouraging, it is important to understand that this is an off-label use of semaglutide medication. While it has shown distinct benefits, it hasn’t been through rigorous testing for safety and efficacy for this specific use. Also, semaglutides are not right for everyone. People with a history of medullary thyroid cancer should not take them. They may not be right for people with some gastrointestinal conditions, such as severe gastroparesis. They can also cause side effects that are worth knowing about. Side effects can include nausea, diarrhea, headache, stomach pain and heartburn.

In making your decision, ask your doctor what research they are using for this recommendation. Ask about the guidelines for its use, and what to do if anything goes awry. You can also get a second opinion from a doctor with experience in PAD if you’re still not sure.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Hello, dear readers! Welcome to a bonus letters column. We hope you had a peaceful and enjoyable holiday season and that this new year (how did that happen so soon?) will treat you well. We have some interesting mail, so on to your letters.

-- We have written several times about the benefits of music for people living with dementia. We have received a number of letters on this topic, including one from a reader in Virginia:

“I was happy to see your article about Alzheimer’s and music. My husband, an emeritus professor at Old Dominion University here in Virginia and an alumnus of UCLA, was diagnosed with Lewy body dementia about 10 years ago,” she wrote. “A brilliant man who knew what was happening to him, he and I watched this destroy his brain. A fellow professor came every week to play guitar with him. To the very end, my husband was able to play his guitar and enjoy music.” Thank you for sharing a tender memory. Music can stimulate neural pathways that often remain intact well after other cognitive functions have been lost. Music allows the person to hold on to a piece of their core self. It also creates a pathway for the shared emotional experiences that are so important to the person’s loved ones.

-- Most recently, we examined new research that suggests listening to music can have a protective effect on cognition. A study from researchers in Australia found that people who made music part of daily life had a 40% lower risk of getting dementia. This protective effect also extended to general cognitive decline. When the music lovers were tested on memory and cognitive function, their results were measurably better than those of the non-music group. Another reader had a follow-up question on this topic.

“I saw your response to a reader about the connection between music and memory, which also tied to a neuropsychiatric/dementia study in Australia,” he wrote. “It was very interesting and it made me wonder: Is there any connection between certain types of music and a lowered risk of dementia?” We were curious about the same thing. At this time, existing research does not suggest that specific genres of music have a more protective effect on cognition. The current consensus is that music in general can have a beneficial effect on the brain, mood and memory. Some studies suggest that up-tempo music, which is more rousing, may engage the mind more directly. But as for whether the classical elegance of Bach may be better than the explosive sounds of Black Sabbath, that research has yet to be done.

Thank you, as always, for taking the time to write. We love hearing from you, and we love to know where you are writing from. For readers whose publications don't include an address, you can reach us at askthedoctors@mednet.ucla.edu. You can also write to us at:

Ask the Doctors

c/o UCLA Health Sciences Media Relations

10960 Wilshire Blvd., Suite 1955

Los Angeles, CA 90024

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)