Hello again, dear readers, and welcome to part two of our monthly letters column. We received so many letters last month that we needed a bit of additional real estate to get to the most popular topics.

-- Regarding the novel coronavirus, we have had several questions about asymptomatic carriers. These are people who, although infected with the virus, have no symptoms of COVID-19, the illness that it causes. “Can you be infected with the virus and not be sick?” a reader asked. “If you don’t have symptoms, can you still get other people sick?” The answer to both questions is yes. Some people can become infected with the novel coronavirus and not experience any symptoms. However, because the virus is replicating within their bodies, they are able to unknowingly transmit it. That’s why, as we’ve discussed here before, it’s so important for us all to wear a facial covering while in public. The virus is broadcast via the tiny droplets of moisture we emit whenever we cough, sneeze, laugh and speak. By wearing a mask, a portion of those droplets are blocked, which protects the people around us.

-- Speaking of masks, a reader asked about whether a mask protects him as well as those around him. “If you’ve got your face covered, won’t that keep the virus away from you, even a little bit?” he asked. “I’m not a scientist, but it just seems like common sense.” The virus, along with the aerosols that carry it, are both so minute that it takes a specially formulated respirator mask to completely block them. These types of masks are in very short supply and are reserved solely for medical settings. Interestingly, a new study from the University of California, San Francisco suggests that tightly woven cloth face masks may -- and the key word here is “may” -- offer a small measure of protection to the wearer as well. Until there is more evidence, though, assume that your mask protects others but not yourself. Remain vigilant about social distancing and hand-washing.

-- A reader who walks her dog every day wonders if her pet puts her at risk. “I’m careful about what I touch, but my dog is ‘barefoot’ on the sidewalk and sniffs everything,” she wrote. “Can you get the coronavirus from your dog?” The Centers for Disease Control and Prevention has good news for you. And we quote: “Currently, there is no evidence that SARS-CoV-2 can spread to people from the skin or fur of companion animals.”

-- We offer a thank-you to a reader from California who wrote in regarding a recent column about lumbar spinal stenosis. It’s a narrowing of the spinal column in the lower back that results in compression of the nerves. We talked about a minimally invasive surgery that uses a small implanted device to act as a lift, and thus create additional space within the spinal column. Our reader pointed out that this type of surgery is known as "minimally invasive indirect decompression" rather than "minimally invasive lumbar decompression." We appreciate the correction.

Thank you again for all of your mail. We look forward to seeing you here soon for our regular letters column.

(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 having trouble sleeping these days, and so is my wife. We’re both 33 years old, we’ve been working from home and we have two very active young sons. What can we do?

Dear Reader: Even before the novel coronavirus upended our lives, poor sleep and insomnia were already affecting millions of people of all ages in the United States. That’s a problem because adequate good-quality sleep is important to physical and mental health and to emotional well-being. People who regularly get fewer than seven hours of sleep per night are at increased risk of a range of health problems, including high blood pressure, heart disease, diabetes, obesity, inflammatory diseases, anxiety and depression. And that’s not even factoring in how lack of sleep affects performance and safety during our waking hours.

It helps to understand that sleep begins at the cellular level. Our bodies respond to the daily 24-hour cycle of light and dark in a number of complex ways. Artificial light disrupts this natural rhythm, as do a host of other factors. These include the blue light from screens, which has been shown to scramble our internal clocks, and substances such as caffeine, nicotine, alcohol, sugar and certain medications. Stress, anxiety and depression, which many of us have in abundance right now, also interfere with sleep. The good news is that there are steps you can take to improve your chances for a good night’s sleep.

Optimize your environment. Make your bedroom as dark and quiet as possible. Window coverings that completely block outside light are a worthwhile investment. Some people swear by a sleep mask. And don’t forget about interior lights, such as clock faces, televisions, and computer, phone and tablet screens. Even those dots of light from chargers and the smoke alarm are better covered up. If noise is a problem, consider ear plugs or a white noise machine. Do what you can to control the temperature. Research shows that people sleep best in a cool room, from 60 to 68 degrees. And we know it’s a challenge, but stop looking at screens a few hours before bedtime. It really makes a difference.

Set a sleep schedule. Be realistic. If you can, match it to your natural preferences for sleeping and waking. Known as chronotypes, these are ingrained sleep-wake cycles that contribute to whether you’re a morning person or a night owl. Include a transitional wind-down time, a personal ritual that signals to your body that the waking day is over. Read a book, do some stretches, give yourself a scalp massage.

Daily exercise can contribute to better sleep. So do meditation and yoga. Many people swear by slow, deep breathing as an effective transition from wakefulness to drowsiness and then sleep. As we mentioned earlier, caffeine and alcohol can interfere with both the quantity and quality of your sleep, so it’s important to stop intake later in the day. Your goal in all of this is consistency, including on weekends. And please be patient -- it can take a few weeks to begin to see results.

(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 always seem to get sick when I start a job. Makes sense -- new people, new germs. I started a job in February, then we all had to work from home. I worry that being isolated for weeks puts me back at square one. What can I do to boost my immunity in preparation for going back to the office?

Dear Reader: We’re always happy to have this particular discussion, because the strategies and habits involved in addressing immune health also tend to lead to improved health overall. The immune system plays an important role in protecting us from all sorts of potential pathogens, and you’re not alone in wondering how to give it an edge.

First, let’s clarify the goal. We hear a lot about “boosting” the immune system, but that’s actually misleading. You don’t want an amped-up immune system. That would mean that it’s hyper-alert and reacts -- and overreacts -- to every perceived threat. Rather, the goal is an immune system that’s healthy and balanced and responds in proportion to the job at hand.

One of the most important steps you can take to keep your immune system happy and healthy involve lifestyle. That is, get an adequate amount of high-quality sleep, take part in daily exercise, don’t smoke, limit alcohol use and eat a healthful diet. When you’re chronically tired, depressed or anxious, overweight, eat poorly, smoke, drink too much and don’t get enough exercise, you’re creating internal stressors that can interfere with optimal immune system response.

Diet plays an important role in immune system health. Emerging research continues to link the health and diversity of the gut microbiome with the health and efficacy of the immune system. We urge our patients to get the necessary vitamins and minerals through food, which we believe the body utilizes more efficiently than supplements. Plenty of fresh vegetables, leafy greens and fruit are crucial to getting a range of vitamins and minerals and to keeping the billions of microorganisms that make up our gut microbiomes well-fed. So are nuts, seeds, beans and legumes. Cultured and fermented foods, such as pickles, sauerkraut, yogurt, kombucha, kefir and miso help with diversity.

We know it’s a challenge, but steering clear of added sugar, sugary soft drinks and highly processed foods is also important to both gut and immune health. Recent studies have shown that regular exercise improves gut health. Sleep is also critical to health and well-being. We’ve had a lot of readers asking for help in this area, and we will revisit the topic in a column in the next few weeks.

We understand that, compared to the vitamins and supplements and products that promise instant immune system magic, this advice sounds pretty dull. But our bodies are intricate and interconnected mechanisms. Everything from circadian rhythms, which are affected by sleep, to the gut microbiome, which is affected by diet and exercise, to mood, which responds to all three, play a role in immune health. Focusing on a whole-body approach, with gradual but consistent changes, goes a long way toward building an immune system that’s balanced and ready to work for 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.)