Dear Doctors: When someone tests positive for COVID-19 now, what are they supposed to do? So much has changed since the pandemic started, what with the vaccines and the boosters and the different variants. Now they’re even changing how long you’re supposed to isolate. I’m confused.

Dear Reader: You are far from alone in feeling overwhelmed by new and changing information as the pandemic continues. We are now two years into what has been a strange and disruptive time. The coronavirus that causes COVID-19 was brand-new to humans when it emerged, which means we’ve had to collect, process and act upon enormous amounts of new information in real time.

Now, with the highly contagious omicron variant driving a spike in new COVID-19 cases -- more than 400,000 new diagnoses in the United State on a recent day -- each of us needs to know what steps to take if we test positive for the virus. First, it’s important to understand that a positive test means that you are infected with the virus and are capable of passing it on to others. This is true even for individuals who are fully vaccinated. If you’re in a public place or around other people when you learn your test results, you should immediately put on a mask. The virus is airborne, and with every exhalation, an infected person puts others at risk.

The next step is a five-day isolation period, during which you have as little contact as possible with others. People who live alone should not venture out. Those living with others -- family or roommates -- need to stay in a single room. When contact is absolutely necessary, it should be as brief as possible, and all involved should wear a high-quality mask. In a household with multiple bathrooms, one should be designated for the infected person’s sole use. If that’s not possible, everyone needs to wear a mask when using the space. An open window and a fan can help with ventilation. The virus is present in stool, so be sure to close the toilet seat when flushing. Sanitize any surface that you touch each time that you touch it.

As of this writing, if you are symptom-free after five days, the Centers for Disease Control and Prevention now says it’s OK to leave isolation. However, you need to avoid close contact with others and continue to wear a mask for another five days. If you do develop symptoms, check with your doctor for specific guidance. The CDC also recommends that people with symptomatic COVID-19 should isolate for at least 10 days.

Anyone who came into direct contact with you while you were infected should immediately begin wearing a mask, and they should continue to do so for 10 days. Two to three days after exposure, anyone who was exposed to you should be tested. If someone subsequently tests positive for the virus, then the isolation and masking protocols apply to them, as well.

Some states have enacted guidelines that differ from CDC recommendations. To be sure you’re following the proper protocols for your particular area, check with your state health department at usa.gov/state-health.

(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.)

Dear Doctors: Our teenage son’s vaping habit has his mother and me quite worried about his health. Nothing we’ve said so far has had any impact. I recently read that vaping can cause erectile dysfunction in young men. Is that true? If so, we may have finally found a persuasive argument for him to stop.

Dear Reader: Although electronic cigarettes were initially developed to help smokers quit, manufacturers quickly developed hundreds of products aimed directly at the youth market.

Nicotine-based e-cigarettes come in a wide array of candy and fruit flavors. Many of them deliver amped-up forms of nicotine beyond what traditional cigarettes contain. Their allure is reflected in the latest National Youth Tobacco Survey, which found that more than 2 million middle and high school students are regular e-cigarette users. Unfortunately, the explosive growth of these products has outpaced their regulation and oversight, which leaves most of their ingredients a mystery.

Nicotine itself is a highly addictive chemical. It can raise blood pressure, increase heart rate, suppress insulin production and promote the buildup of plaque in the artery walls. Propylene glycol, which is one of the delivery agents in e-cigarettes, is used in the manufacture of solvents, antifreeze and the artificial smoke in fog machines.

E-cigarettes are still relatively new, so facts about the short- and long-term health effects of inhaling the chemicals they contain are just beginning to emerge. This includes research that links inhaling the heated tobacco vapor of an e-cigarette to increased risk of developing asthma and chronic obstructive pulmonary disease. And now, as you’ve mentioned in your letter, a new study has tied vaping to erectile dysfunction, or ED.

According to researchers at New York University, the use of e-cigarettes doubled the risk of ED in men age 20 and older. The findings, published last fall in the American Journal of Preventive Medicine, were based on two years of data collected in a federally funded study into smoking habits and health outcomes in the U.S. Of the 13,700 men who answered a question about ED, those who used e-cigarettes every day were more than twice as likely to experience erectile dysfunction as were those who had never vaped.

Previous studies have drawn a strong connection between both smoking and nicotine to ED. This is due to the effects of nicotine, as well as the thousands of chemicals present in cigarette smoke, on the vascular system. However, the higher likelihood of ED in the regular vapers was a surprise. So was the lower end of the age range. Studies in rats have linked the chemicals in e-cigarette liquids with low sperm count and low testosterone in men, which may be playing a role.

While the severe lung injuries that were in the news a few years ago were linked to black market cannabis products, nicotine-based e-cigarettes are far from harmless. Persuading a teen to change his habits already is hard enough without a highly addictive substance in the mix. We hope the new information about the link to erectile dysfunction will help you make your point.

(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.)

Dear Doctors: What happened with those identical twins -- I think they’re well-known marathon runners -- who did a study about how their bodies would change if one ate more meat and one went vegan? Did it wind up proving anything?

Dear Reader: The unique attributes of identical twins, who share all of their genes, have long made them valuable subjects for a wide range of research. This is particularly true in questions about whether genetics or environmental factors play a more significant role in specific scenarios.

The brothers you’re referring to are Ross and Hugo Turner, identical twins from England. They are athletes and adventurers who, over the years, have taken part in experiments pertaining to their training regimens. Some of these, including the one you’re asking about, have been overseen by the Department of Twin Research at King’s College in London.

In that study, the twins each followed a different diet for 12 weeks. Ross ate a diet that favored meat, fish and dairy, while Hugo’s was completely plant-based. To limit the variables, the brothers consumed the same number of calories per meal and followed the same exercise regimen. Researchers from King's College kept track of health metrics during the three months of the experiment. These included weight gain or loss, changes to blood lipid levels and gains or losses of muscle mass. The brothers also wore glucose monitors to measure blood sugar, and they kept track of how they felt physically and mentally.

In the first month of the experiment, the vegan brother lost 9 pounds. However, he regained some of that and finished with a net 4-pound weight loss. He also lost a full percentage point of body fat, going from 13% to 12%. His cholesterol levels dropped significantly during the three months, and his blood glucose control improved.

Meanwhile, the meat-eating brother gained 10 pounds, including several pounds of fat, during the experiment. Although his body fat percentage rose from 13% to 15%, his cholesterol level stayed the same. His blood glucose control was not as good as his brother’s, and he reported feeling dips in his energy levels in the late afternoon.

When it came to changes in the gut microbiome, there were some surprises in store. The diversity of the meat-eating brother’s gut microbiome remained about the same, while that of the vegan brother measurably decreased. Although the experiment wasn’t designed to explain that change, the researchers suspected that removing fermented milk products, such as cheeses and yogurt, may have played a role. The vegan brother’s gut flora also changed in ways that improve resistance to Type 2 diabetes.

It’s important to note that results of a 12-week experiment with just two subjects are hardly conclusive. However, the findings are in line with larger and more rigorous studies. Nutritional research continues to point to the benefits of a balanced diet made up of lean proteins, including fish and other seafood, healthful fats, fermented foods and a wide variety of colorful fruits and vegetables. It’s good for the heart, improved blood-sugar control, gut microbiome diversity and better health overall.

(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.)