Dear Doctor: Your column about long-haul COVID-19 started a conversation at our house about why some viruses will keep getting you sick even after you’ve recovered. A friend of our family is having a hard time with something called post-polio syndrome. Is that the same kind of thing?

Dear Reader: You’re not alone is seeing the similarities between long-haul COVID-19 and post-polio syndrome. We recently heard from a reader in Bucks County, Pennsylvania, who wrote to say that people with post-polio syndrome have great empathy for COVID-19 long-haulers and understand the challenges that these people face.

As a recap, long-haul COVID-19 refers to the ongoing adverse health effects of coronavirus infection, which can last for weeks, and even months, after the initial phase of their illness has passed. Symptoms include persistent fatigue or exhaustion; ongoing shortness of breath; heart arrhythmias, including a racing heartbeat; pain in the muscles and joints; and headache. Many patients report difficulties with concentration and memory, which they refer to as “brain fog.” Some experience uneven recoveries in which they appear to be on the mend but relapse into illness again.

Post-polio syndrome, by contrast, arises years later, usually a decade or more after the initial illness. The condition makes itself known with a gradual weakening of the body as a whole, and of the specific muscles and muscle groups that had been previously affected by the polio infection. In some cases, the muscles may also begin to atrophy, or decrease in size. Physical changes to the joints may also take place. Some people experience trouble with breathing, become sensitive to hot or cold temperatures, and may develop sleeping disorders.

Both long-haul COVID-19 and post-polio syndrome occur only in a subset of survivors. There are believed to be about 300,000 polio survivors in the U.S., and from one-fourth to one-half of them may experience some degree of post-polio syndrome. Long-haul COVID-19 is so new that we don‘t yet know how often it occurs, but it may be as many as 20% of patients with COVID-19. People with either syndrome may experience only mild symptoms, or they can find themselves dealing with what is essentially a new and ongoing illness.

As for why these viruses continue to affect people after the initial infection has passed, the answers are not yet clear. When it comes to post-polio syndrome, one theory suggests that the patient’s recovery from the initial paralysis involved the regrowth of new nerve pathways, which then become overtaxed as the years pass. Newer thinking suggests that the polio virus may go dormant within the body, and then, for reasons that are not yet understood, reactivate years later.

With long-haul COVID-19, new research from scientists at the University of California, Davis, suggests that the ongoing respiratory and cardiac effects arise from lung damage sustained during the initial illness. In relapsing cases of COVID-19, it has been theorized the immune system is continuing to encounter fragments of the virus and mounting a defense that results in another round of symptoms. The hope is that, as research continues, effective treatments for long-haul COVID-19 will be found.

(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.)

Hello, again, dear readers. We’re back with the second of our two bonus letters columns. Let’s dive right in.

-- After a column that referenced magnesium, we heard from a reader from Deltaville, Virginia, whose wife had been diagnosed with very low levels of the essential mineral. “What actually causes low magnesium levels?” he asked. “What can be done about it other than the four-hour infusion sessions she is going through?” Magnesium plays a role in hundreds of chemical reactions throughout the body and is crucial to heart, muscle, nerve and kidney function. Low levels arise from poor absorption, or excessive excretion, of the nutrient. Conditions such as chronic diarrhea; kidney disorders; and high levels of certain hormones, including thyroid hormones, can all increase magnesium excretion. So can the overuse of certain types of antacids. People with gastrointestinal issues, such as celiac disease or Crohn’s disease, are often unable to adequately absorb magnesium. Some medications can also interfere with absorption. Infusions are used when deficiencies are quite severe. As levels stabilize, a switch to oral magnesium supplements may be adequate.

-- Speaking of magnesium, a reader from Rye Beach, New Hampshire, wrote in response to a column about restless leg syndrome, or RLS, a condition that causes an irresistible urge to move the legs. “Please suggest a simple and inexpensive mineral that’s important to the whole body -- magnesium,” she wrote. Although it doesn’t work for everyone, some people with RLS do find that increasing magnesium in the diet can help ease symptoms. As with all supplements, check with your health care provider for guidance. Taken in large amounts, magnesium supplements can be unsafe and can lead to side effects such as heart arrhythmias, low blood pressure and impaired breathing.

-- In response to a column about persistent hiccups that last for weeks, or even months, a reader from Spokane Valley, Washington, shared an unexpected avenue of relief. “My mother had those hiccups,” she wrote. “A friend of the family suggested she go to a chiropractor. She did, and the hiccups went away and never came back.” Persistent hiccups, while rare, interfere with quality of life. We aren’t aware of any studies that back up a chiropractic approach to dealing with hiccups. However, there is anecdotal evidence from patients who say that visiting a licensed chiropractor has offered relief.

-- A reader from Fresno, California, asked for help with compression stockings. “I’m 89 years old, have poor circulation and am allergic to compression stockings,” she wrote. “I walk a mile every day, and the stockings would be helpful.” It’s possible that you’re allergic to latex, which gives many brands of compression stockings their stretch. The good news is that some brands of compression stockings are latex-free. We think it would be a good idea to give them a try and see if you have better results. Meanwhile, congratulations on your impressive fitness regimen -- you’re an example to us all.

Thank you to everyone who writes to us. We look forward to hearing from more of you, and will be back with our regular letters column next month.

(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.)

Hello, dear readers, and welcome to an extension of our monthly letters column. Our main letters column this month was devoted to your questions about the new coronavirus vaccine -- an important topic that needed immediate attention. So we’re back with parts one and two of a bonus edition to help catch up with your more general questions. Onward to part one!

-- A reader from Cleveland asked if eating carrots helps with prostate health. “Have you ever heard of this?” he asked. “How many carrots do you have to eat?” While a potential link between eating carrots and prostate health has been a subject of interest for a number of years, the research remains inconclusive. Some studies have found a link between alpha-carotene, a nutrient in carrots, and a decrease in prostate cancer risk. The studies found eating a medium-sized carrot each day, or drinking freshly pressed carrot juice, to be helpful. However, those results haven’t been universally duplicated. If you’re going to try it, we recommend eating your carrots, because the crude fiber they contain is beneficial to the gut.

-- In a column about why falling is a serious health risk for older adults, a reader from Fresno, California, asked for a clarification. “You wrote that just a sprain or a bruise can interfere with quality of life,” she wrote. “Can you elaborate?” Although a big concern with falls is breaking a bone, even a mild injury can alter someone’s routine. A sprained ankle makes it difficult to get around. Small tasks like going to the mailbox, or even walking from room to room, can become daunting. The aches and pain of a bruise can limit movement, so basic actions like reaching up to a kitchen shelf or dressing oneself become more difficult. These limits are temporary, of course, since sprains and bruises heal. But, in the meantime, daily life is adversely affected.

-- A reader near Austin, Texas, who recently cared for her father and two aunts at the ends of their lives, noticed that dentists would sometimes suggest procedures that were out of step with the needs and abilities of an older adult. “Do keep up with cleanings and care for cavities, but get a second opinion for things like tooth extractions and implants,” she wrote. “Some older senior citizens may not be healthy enough for these procedures, which the dentist may not know, or they may not have the money to afford them.” We think that’s very good advice. A second opinion can clarify a medical or dental issue and help ensure that only necessary care is performed. Thank you for sharing.

-- A reader from Tulsa, Oklahoma, got right to the point with his question: “Is it possible for mosquitoes to pass on COVID-19?” So far, there are no known cases of the new coronavirus being transmitted via a mosquito bite. It’s a respiratory virus, and its main form of transmission is through the droplets from a cough or sneeze and the smaller particles released when we speak or exhale.

See you in a few days with bonus questions in part two.

(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.)