Dear Doctor: I've been hearing about adenovirus, which is often mistaken as the flu. How can you tell the difference? And is it as serious as the flu?

Dear Reader: Your question is a great reminder, especially during flu season, of how complex and ubiquitous viruses are. They cause a host of illnesses, with the common cold alone blamed on more than 200 identified subtypes of virus and many more that are still unidentified. One main group of viruses is adenovirus.

Adenovirus got its name because it was first isolated in the adenoids, although this isn't the only place it's found. More than 60 types of adenovirus exist, with some causing much different symptoms than others. Serotypes 3, 5, 7, 14 and 21, for example, have been associated with more severe disease.

Adenoviruses most commonly cause upper respiratory symptoms. These include inflammation of the throat, leading to a sore throat, and swelling of the membranes in the nose, leading to runny nose and nasal congestion. Such symptoms are often accompanied by headache, fever, fatigue, muscle pain and stomach pain.

But adenovirus can also lead to conjunctivitis, laryngitis, bronchitis and even pneumonia. Adenovirus-caused pneumonia more often affects those younger than 5 years old, accounting for 15 percent of pneumonias in this age group. Young children can also be affected by subtypes of adenovirus that lead to diarrhea, which can last up to eight to 12 days.

In rare cases, the virus can affect the brain, causing meningitis or encephalitis, or lead to inflammation of the liver and the heart muscle. In people with a compromised immune system or those who have had an organ transplant, adenovirus can lead to more severe disease and possible death.

Adenovirus is a resilient virus. It can survive for long periods on environmental surfaces and -- though bleach, formaldehyde and heat can inactivate it -- the virus is resistant to many disinfectants. It can be transmitted through respiratory droplets spread by sneezing, coughing or contact with secretions. Adenovirus is also shed in the stool for many weeks after an acute infection. Without proper handwashing by all parties, the virus can then be taken in orally by another individual.

Because adenovirus is easily transmissible, it's associated with outbreaks of infection in day care settings and among military recruits. In fact, military recruits are now vaccinated against adenovirus, which has decreased their rate of infection.

Adenovirus is diagnosed by either viral culture or by tests producing more rapid results. The treatment is similar to those for other cold viruses -- fluid intake, rest, acetaminophen or nonsteroidal anti-inflammatory drugs (aspirin, ibuprofen) for headache and medications for diarrhea. For people who are taking drugs to suppress the immune system, the antiviral medication cidofovir can improve survival.

Yes, many of the symptoms are similar to influenza, especially in young children. The fever in those under 5 with adenovirus averages 102.6 degrees. This is similar to influenza. However, influenza is a much deadlier virus, especially among older individuals, causing thousands of deaths per year. Although adenovirus can cause significant illness, it doesn't usually lead to the intensity of sickness and the death rates seen with flu.

Rapid flu tests can help distinguish whether a specific illness is due to influenza or another virus, such as adenovirus, but the point remains: If a person becomes dehydrated or if his or her mental state changes, seek emergency help. Neither illness should be taken lightly.

(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: I'm a 75-year-old man who's done hard physical farm labor since I was a young boy. Now I have painful tingling, burning and numbness in my right palm and fingers. It disrupts my sleep and makes it difficult to hold a pencil. A hand brace doesn't help. Is it carpal tunnel syndrome? What can I do?

Dear Reader: Of course, I can't make a diagnosis without a proper examination -- and I would encourage you to seek one from your physician -- but your symptoms have all the hallmarks of carpal tunnel syndrome. This syndrome occurs because of compression of the median nerve at the wrist. As you look at the wrist with the palm side up, feel the multiple tendons in this portion of the wrist. The median nerve has to share space in the area called the carpal tunnel with nine of these tendons. When the wrist or the tendons within the carpal tunnel become inflamed, the median nerve gets compressed.

Because the median nerve supplies sensation to the thumb, index and middle fingers, compression of it can cause abnormal sensations, such as tingling, burning or even a loss of sensation. The median nerve also helps control the muscles of the thumb and, to some degree, the index and middle finger, so compression can lead to a loss of coordination and difficulty holding objects with the hand. This is most evident when using the thumb to hold an object such as a pencil or a cup. Many people with carpal tunnel syndrome have reported dropping cups.

The burning/tingling sensation in the hand is often noted upon waking -- sometimes causing the waking -- because the hands tend to flex at the wrist during sleep, leading to compression of the median nerve.

Repetitive and forceful use of the hand and wrist is a primary risk factor for carpal tunnel syndrome, as is working with tools that vibrate or that keep the hands in a fixed posture. Lifelong work in farm labor does have physical benefits, but it can take a toll as well.

Additional risk factors include diabetes, low thyroid hormone levels and rheumatoid arthritis, all of which can lead to carpal tunnel syndrome.

A wrist brace is a good first treatment for carpal tunnel syndrome because it stops the hand from flexing at the wrist, further compressing the median nerve. The next step would be physical therapy, though you should continue to use the brace at night. Treatments such as acupuncture and ultrasound therapy have shown some benefit in easing the symptoms of carpal tunnel syndrome, but more study is needed.

Steroid injections into the wrist can decrease swelling around the median nerve, usually providing a short-term benefit of one to three months. Physical therapy can enhance the benefit, but truly lasting improvement will generally occur with surgery that opens up the space around the median nerve.

Follow up with your doctor regarding these symptoms. He or she may suggest nerve-conduction studies to verify carpal tunnel syndrome and recommend a specific therapy that meets your needs.

(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: I'm hearing a lot about the health benefits of a ketogenic diet, that it's great for weight loss and can even reverse diabetes. What is the diet, exactly? Are the claims true?

Dear Reader: The ketogenic diet, widely known as "keto," is an eating plan that switches an individual's main energy source from carbohydrates to fat. In its strictest form, 80 percent of calories come from fat, 15 percent from protein, and carbohydrates are limited to 5 percent of the total daily food intake. Considering that most Americans get about half of their daily calories from carbohydrates, 15 percent from protein, and about one-third from fat, keto basically flips the typical American diet on its head.

The name comes from the word "ketosis," the metabolic state that arises from this particular distribution of nutrients. When adequate carbohydrates are available, the body turns them into glucose, which it uses for energy. With carbs missing in action, the body switches to Plan B -- its stored fat. Burning that fat creates an energy source known as ketones. This shift takes place over the course of the first few days of limiting carbs to the 20- to 50-gram range. (Some dieters opt to jump-start the process with a 24- or 36-hour fast.)

People on a ketogenic diet eat mainly meat, fish, eggs, full-fat dairy, oils and low-carb vegetables, like leafy greens. Because of their high carb count, fruit, root vegetables, corn, grains, cereals and legumes don't make it onto the plate. Needless to say, pasta, rice, bread, and sweets become a thing of the past. In fact, with carbs restricted to about 20 grams per day, a single apple or banana will blow your carbohydrate budget.

While the extreme nature of the keto diet makes it sound like a fad, it was actually introduced in the 1920s to help children with medication-resistant epilepsy. Ongoing research suggests the diet may be neuroprotective, and scientists are looking into its potential to help patients with neurodegenerative diseases like Parkinson's and Alzheimer's disease.

You're right that the keto diet has been shown to improve glycemic control in people with Type 2 diabetes. Some patients do go on to reduce or even discontinue their medication. However, the diet's effect on blood chemistry can be extreme enough to require rapid adjustments in medication levels. People with Type 2 diabetes should not attempt it without a doctor's supervision. The diet is not recommended for people with Type 1 diabetes.

And while those on the keto diet experience rapid weight loss, they're also subject to constipation, electrolyte imbalances, nutritional deficiencies, poor mood and just plain boredom. Our main concern is the high fat content. Despite a dieter's best intentions to stick to good fats, the focus on high fat inevitably leads to excessive bad fat consumption. One of our patients wound up with LDL levels that doubled, which is never a good thing.

You've heard this from us before, but seriously, please check with your doctor before going keto. And if you do decide to give it a try, it would be wise to work with a nutritionist to craft the most well-rounded version of the diet possible.

(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.)