Question: It seems that after my daughter has a busy workday she develops a hoarseness. She finds it difficult to speak during the evening. I am concerned that this is something that needs medical attention. Should she see a specialist?

- R.B.

Answer: Hoarseness lasting more than three weeks cries out for a thorough examination of the vocal cords. Hoarseness often has a viral origin, but three weeks is about as long as any ordinary viral infection lasts.

Beyond three weeks, we would look at other possible causes - some grim, some not.

Cord polyps, nodules and cancer can cause hoarseness, but often there is a correctable chronic irritant involved. Vocal cord spasms can create intermittent hoarseness. And there are the routine causes associated with shouting and all the other activity related to some fields of work or the environment.

Your daughter should see a specialist, a laryngologist (LAR-in-GOLL-oh-jist).

Meanwhile, she should not try to mask her hoarseness by whispering. Forced whispering actually places greater stress on the cords than does speaking normally. Your daughter should rest her voice completely in the evening and speak when necessary in a muted but confident tone.

Humidifying the air can help relax the vocal cords and reduce the swelling that can accompany hoarseness.

Question: Please write about hepatitis B virus. What is it? How could I have gotten this virus? I am a woman, 60, and I was told not to donate blood anymore.

- L.G.

Answer: The handful of viruses that cause liver inflammation and liver cell damage differ one from another in behavior and in potential for mischief.

How did you get the B virus? Easy answers seldom are forthcoming to that question. Contaminated transfusion blood used to be a source, but we screen for the virus carefully these days. The blood bank's admonition to you is assuring on that score, isn't it?

The B virus can pass from the mother to child during pregnancy. It can be transmitted sexually and in certain health-care situations. It's a common hazard for health-care workers. Blood contaminated with the B virus can be transmitted from a patient to a healthy person by an inadvertent needle stick.

Some B-positive people never have a clue as to how they got that way.

You want to determine if the virus is doing any current liver damage. If it is causing damage or has in the past, your doctor can evaluate the situation. Interferon can be prescribed if liver damage is great or ongoing.

Report the blood-bank-test finding to your doctor, who can tell if you are a carrier or if you need treatment right away.

For more information on hepatitis, see the Health Letter report on the subject. For a copy, write Dr. Donohue - SR145, Box 5539, Riverton, NJ 08077-5539. Enclose $3 and a self-addressed, stamped (55 cents) No. 10 envelope.

For K.C.: We have no medicine yet for infectious mononucleosis. All we can do is try to make the patient as comfortable as possible. Your school friend might find that gargling with warm salt water takes some of the pain from the throat.

I often am asked about a mono vaccine. I must say that we have not yet come up with that either. Researchers are working on it, though.