Dear Doctor: How does the flu virus spread? I've always thought it was mostly from coughing, which contaminates the air and the surfaces we touch. But now I've heard that people who are sick actually breathe the virus out. Should I be wearing a mask to protect myself?

Dear Reader: One of the more challenging points to get across regarding the flu has been just how contagious a sufferer is, and how early into a bout of the illness that contagion begins. Now comes research that makes understanding (and acting on) this information all the more crucial.

You're correct that the assumption has been that it's by coughing that we pump aerosolized droplets of moisture, which contain the flu virus, into the air and onto the surfaces around us. We've known for some time that these droplets can hang in the air for up to several hours and can live on hard surfaces for several days. But the results of a recently published study by scientists at the University of Maryland's School of Public Health show that by simply breathing, a person who is sick with the flu is exhaling the virus.

The researchers examined the mechanics of how 142 university students with confirmed cases of influenza sent the virus into the air around them. The participants in the study sat in front of a device that could measure various sizes of the aerosolized droplets they dispersed while coughing, sneezing, talking or breathing. In 218 sessions that lasted 30 minutes each, it was revealed that close to half of the airborne droplets that contained the flu virus were collected in the absence of coughing. Since the participants rarely sneezed, the takeaway was that people with an active infection are dispersing the virus into the air around them when they breathe.

An earlier study from the University of Hong Kong concluded that half of flu infections within households are passed along via aerosolized droplets. The study also looked into your question of whether wearing a surgical mask would prevent infection. The answer echoes the findings of several similar studies -- basically, no. Though masks may slightly reduce risk by screening out the largest droplets, they are not effective against the fine aerosolized mist from the breath. According to the Centers for Disease Control and Prevention, the people who really should be wearing facial masks are individuals who are ill.

It's important to note that the University of Maryland study did not tackle the specific question of how the flu is transmitted. Still, the findings do suggest that, even in the absence of coughing, people with the flu can send the virus into the environment around them.

All of which leads to advice that physicians have been giving -- and which patients have been ignoring -- for generations. And for emphasis, we're putting it into a paragraph of its own:

Stay home when you're sick.

Not only do you really and truly need to rest in order to give your body the best shot at recovering from influenza, but venturing forth while you're actively ill puts everyone around you at risk.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: What can I do about persistent, intermittent rectal itch? I keep the area clean and dry and have tried numerous over-the-counter anti-itch medications, which seem to work for a short time before becoming ineffective. My primary care physician gave me an anti-fungal prescription (clotrimazole with betamethasone), which my dermatologist said was unwarranted. Your suggestions?

Dear Reader: Kudos to you for being willing to talk about this annoying symptom that most people don't like to acknowledge, even to their doctors. Be assured: Anal itching (pruritus ani) is a common condition affecting 1 to 5 percent of the population. It's four times more common in men than in women and occurs predominantly between the ages of 40 and 70.

As for why the condition occurs, it's generally due to small amounts of fluid stool that irritate the anal region. This may be because the stool itself is loose or because the anal sphincter is abnormally relaxed, allowing leakage. In both cases, fecal material irritates the area beyond the sphincter and causes itching, leading to excessive wiping or scratching of the region. A 1982 study found that 50 percent of people with anal itching normally had loose stools and that 41 percent lost small amounts of stool at least one day a week. Of note, coffee has been found to relax the sphincter in 70 percent of people with the condition.

Other factors can lead to pruritus ani as well, with fungal infections accounting for 15 percent of episodes. People with diabetes, those who are taking medications that suppress the immune system and those who have used multiple courses of antibiotics are at increased risk of this type of infection.

Bacterial infections can also cause anal itching. So can chemicals from soaps, creams or wet wipes, either through direct irritation or through an allergy to these products. Hemorrhoids and psoriasis can be factors too.

The first step in treating pruritus ani is to eliminate practices that irritate the anal region. Start by washing the area -- without soap -- to remove any retained material. This can be done with a bidet, or through showering or bathing. Other steps: Use softer, more absorbent toilet paper to make wiping less irritating; make sure the anal area is dry before putting on underwear; and use a zinc oxide cream to help heal the anal area and create a barrier against further irritation.

As for food and drink, not only has coffee been associated with anal itching, other foods and beverages have also been implicated. These include beer, cola, caffeinated tea, chocolate, citrus foods and drinks, tomatoes, chocolate, peanuts and grapes.

The antifungal preparation that your primary care doctor recommended includes a mixture of antifungal and steroid compounds. The steroid betamethasone eases the itching, and the clotrimazole cream acts against any existing fungal infection. However, strong steroid creams can cause skin thinning in the anal region, potentially leading to further irritation and itching.

In summary, take a hard look at the foods and drinks you're consuming; remove irritating soaps or wet wipes; use water to clean the anal area; keep the area dry; and use a zinc oxide cream to help healing. By following these strict habits, you just might be able to rid yourself of this annoying symptom.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Hello again, dear readers, and welcome to another edition of our ongoing conversation. We're very happy that, a little more than a year into our column, we continue to hear from you. How are your New Year's resolutions faring thus far? If you have any success stories, or thoughts on how to stay (or get back) on track, we'd love to hear them.

-- We've received a lot of feedback on the column about nurse practitioners (also referred to as NPs) and physician assistants (also known as PAs). Several letter-writers corrected our use of an apostrophe in referring to the profession of physician assistant. It may seem trivial but in fact there's a crucial difference between "physician's assistant" and "physician assistant," and it's about autonomy. A physician assistant is a clinician in her or his own right. We regret (and won't repeat) the error.

-- In that same vein (and in the same column) we neglected to fully state the educational requirements to become a nurse practitioner.

Vicki, whose daughter is a NP, filled in the details:

"Nurse practitioners must have a Master of Science in nursing," she wrote. "At the University of Memphis, the NP must take an exit exam about four weeks prior to graduation (with a passing grade), or you don't graduate with that class (extra pressure!). Once the exit exam is passed, the NP has to take state boards to actually become licensed."

Sandra, an Advanced Practice Registered Nurse (APRN) in Kansas, points out that a Master of Science is, in fact, the minimum educational requirement for a nurse practitioner:

"In our state, NPs will no longer be able to enter practice with a master's degree," Sandra wrote. "Entry into practice will require a doctorate, usually a DNP -- Doctorate of Nursing Practice. In addition to the undergraduate nursing degree, NPs have hands-on nursing practice prior to going on to advanced practice, which requires hundreds of hours of clinical training."

And Rich, a physician assistant in Massachusetts, wrote to say NPs and PAs are integral to the functioning of most hospitals and medical centers:

"Many NPs and PAs work in ICUs, often seeing the most complex patients, so this work is not just left to doctors. As any new resident in the ICU will tell you, it's an experienced ICU nurse who helps guide inexperienced interns and residents through the ICU, and likely other rotations as well. Medicine is more team-oriented today than ever before.

"Also, more and more academic medical centers have residency programs in oncology, surgery, cardiology and other fields of medicine for PAs, so they can get advanced training."

We thank all the nurse practitioners and physician assistants who took the time to write regarding the column. One thing the letters had in common was a deep passion for medicine and an even deeper concern for the patients you treat. We agree with you that the practice of medicine is a calling, and we are both proud and honored to be your colleagues.

For readers who want to learn more about these specialties, visit the American Association of Nurse Practitioners at aanp.org and the American Academy of Physician Assistants at aapa.org.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)