DEAR DR. DONOHUE: I am worried about my husband, who is 82 and in poor health. He hasn’t been able to get a flu shot this year. What can we do if there’s an outbreak? – R.D.

ANSWER: The scarcity of flu vaccine has put many in a dither, but the vaccine is not the only way to prevent the flu.

First off, it is important to realize what flu – influenza – is. It’s a respiratory infection, not a digestive tract one. “Stomach flu” — vomiting, diarrhea and abdominal cramps – is a misnomer. It’s not due to the flu virus, and the flu vaccine doesn’t prevent it.

Real flu is an illness with an abrupt onset. Stricken people feel fine one minute, and the next they are miserable. They develop a fever, something that helps separate flu from the common cold. Flu produces a dry, hacking cough. The nose might run, but not as much as it does with a cold. Muscles hurt, and people feel so rotten that they take to their beds.

There are four anti-flu medicines: Symmetrel (amantadine), Flumadine (rimantadine), Tamiflu (oseltamivir) and Relenza (zanamivir). The first three are oral medicines, and Relenza is a medicine taken through a mouth inhaler.

All four lessen flu symptoms and shorten its course. Symmetrel, Flumadine and Tamiflu can be taken to prevent the flu. When there is an outbreak in the community, unvaccinated people can avail themselves of one of these medicines and be pretty sure they will not catch the flu.

Your husband is not left without a life preserver.

DEAR DR. DONOHUE: I have some flu questions for you. How effective is the vaccine? How long does it take before it begins to work? When a person has the flu, for how long can he or she spread it? If one comes down with the flu, how long does it usually last? – V.L.

ANSWER: Flu vaccine is a dependable vaccine. It has a success rate in preventing flu 70 percent to 80 percent of the time. It is not as effective in elderly people as it is in the young, but it does minimize flu symptoms in the elderly and reduces the risks of serious complications and death.

It takes between two and six weeks to build up antibodies after a flu vaccination. Antibodies provide the protection against infection.

The incubation for flu – incubation being the time from catching the flu virus to the time when symptoms appear – ranges from one to four days. Infected people can pass the virus to others from one day before the onset of symptoms through the fifth day of illness. Children can spread the virus longer – 10 or more days after they develop symptoms.

Typically, flu lasts a week to 10 days. Cough and the dragged-out feeling so typical of flu can persist for two or more weeks after that.

DEAR DR. DONOHUE: I had my spleen removed in 1980 after getting hit pretty hard playing softball. I was told by my surgeon at that time never to take a flu shot because I no longer had a spleen. I went to another doctor last winter and asked about a flu shot. She agreed with the surgeon and said not to take one. I recently went to another doctor, who is now our family physician, and asked him about a flu shot. He said he did not know why the other doctors said not to have one, and he suggested I take one. I don’t know what to do. Any advice? – D.A.

ANSWER: People who don’t have a spleen are at risk for infections from certain bacteria. The pneumococcus bacterium, the most common cause of bacterial pneumonia, can cause big trouble for those without a spleen, and they should be vaccinated with the pneumococcal vaccine, commonly called the pneumonia shot.

Viral infections, like the flu, are not a great threat for those without a spleen. However, that doesn’t mean these people cannot have flu vaccine. The Centers for Disease Control and Prevention annually publishes recommendations for flu vaccination. Nowhere in its publication does it say that people without spleens should not get the flu vaccine — the inactivated vaccine, the one given by a shot. I side with your third doctor.

DEAR DR. DONOHUE: I am just getting over diverticulosis. I had to be hospitalized and was treated with intravenous fluids and antibiotics. The doctor said I might need surgery and have to wear a bag on my stomach. How can I prevent another attack, and how did I get it in the first place? – R.R.

ANSWER: In parts of the world where there is little fiber in the diet, many people come down with diverticulosis. A diverticulum is a pea-sized bulge of the colon lining that has pushed through the muscular colon wall. Without a good fiber supply, undigested food dries out. It takes great force for the muscles of the colon to push the dried food residue along for eventual evacuation. The force, in turn, causes bits of the colon lining to project through colon wall as diverticula.

You had more than diverticulosis. Diverticulosis is simply the presence of diverticula. In our society, close to 20 percent of the population have it by the time they are 45, and 80 percent have it by the time they reach 85. Diverticulosis is usually a silent condition. However, inflammation of the diverticula – diverticulitis – is a painful condition. That’s what you had.

Most of the time, resting the colon by putting patients on clear fluids orally or bypassing the digestive tract with intravenous fluids can soothe the inflamed diverticula. Antibiotics are administered at the same time. Only when complications occur is surgery necessary. Complications include a perforation of a diverticulum with leakage of bowel contents into the abdominal cavity. The surgery is often a two-stage affair. In the first stage, one end of the colon is brought to the surface of the abdominal wall, and fecal material is diverted into a moisture-proof bag. Three months later, the second stage is done. It consists of reattaching the colon to the rectum, and the need for a bag is gone.

To prevent the formation of more diverticula and the possibility of diverticulitis, increase the amount of fiber in the diet. Whole grains, bran and fruits with their skins are good fiber sources.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.