With national concern growing over acts of bioterrorism, Dr. Henry Rosen answers readers' questions about smallpox, anthrax and other such threats.

Rosen is associate chairman of the University of Washington Department of Medicine and an expert in infectious diseases. He did his undergraduate work in mathematics at Yale and received his doctor of medicine from the University of Rochester in New York. He received advanced training in internal medicine and infectious diseases from the UW and has been on the university faculty for more than 20 years. He is an associate editor of the Journal of Infectious Diseases.

Q: I have had three smallpox vaccinations in my life. One as a baby, one about 1961 and the last one about 1971. Is it possible that I have any immunity to smallpox at this time?

— Dottie Pinneo, Kirkland

A: Current wisdom is that, after 10 years from the last vaccination, smallpox vaccinations are of uncertain effectiveness. The Centers for Disease Control and Prevention puts it as follows:

"The level of immunity, if any, among persons who were vaccinated before 1972 is uncertain; therefore, these persons are assumed to be susceptible."

The emphasis on "assumed" is mine. Vaccination programs were stopped in the U.S. in 1972 because smallpox was no longer considered a public-health threat in this country. Some level of immunity (milder disease or even complete protection) from your old vaccinations is indeed possible but simply cannot be claimed with assurance. There have been no natural smallpox infections anywhere in the world since 1977.

Q: Anthrax is described as having "coldlike" symptoms. But it also seems to include vomiting, which is not a symptom of cold, or even of flu. Is there anything that might alert people that this is not a regular flu or cold?

— Elizabeth J. May, Seattle

A: Inhalation anthrax does not readily distinguish itself from common respiratory infections until the later, very grave, stages of the disease. However, runny nose and coughing up phlegm are NOT characteristic of inhalation anthrax and would suggest other reasons for one's symptoms. In this sense, runny nose and phlegm production would be "good."

Initial symptoms of inhalation anthrax are those of feeling generally bad (malaise) and experiencing fatigue, muscle aches and fever. If there is cough, it is usually dry — that is, there is no phlegm. There also may also be some mild chest discomfort. These symptoms are common and can be caused by lots of "ordinary" infections. This is why the illness is so difficult to detect early.

Later in the illness chest pain may be substantial. Swollen lymph glands, deep in the chest, may make for an abnormal chest X-ray. The lymph-gland swelling can press on the airways so that drawing a breath becomes difficult and patients may be short of breath.

Q: Are area doctors being briefed to culture patients that could potentially be the heralds of an expanded anthrax problem? I am not in favor of unnecessary antibiotics and do not wish to be placated by a physician, but I have real concerns for the well-being of my family and wish to do whatever I can to ensure their health given the current state of our nation. The biologist in me (I am a secondary schoolteacher) is realistic enough to know that whoever is in "the first wave" will be the ones least likely to get treatment and survive. Once identified in our area, I am confident that proper culturing would occur. Any suggestions to put my anxiety to rest would be greatly appreciated.

— Teresa Coda, Renton

A: I believe that your concerns about the first people to get anthrax in a community are well placed. It would be very difficult to make a timely diagnosis of inhalation anthrax in a setting where no anthrax had appeared before.

Flu shots may protect from the flu (influenza A virus) but would not protect from other respiratory viruses that can cause similar symptoms. Thus many individuals each winter will develop "flu" symptoms regardless of their flu-vaccination status. Some of these people may be anxious about inhalation anthrax but would be highly unlikely, on statistical grounds, to have the disease they dread.

There is no reliable laboratory diagnosis for early inhalation anthrax. Cultures are effective and reliable only for skin anthrax and for late stages of either skin or inhalation disease.

The main reassurance that I am able to draw from events, to date, is that so few individuals have been seriously infected. Awareness of the disease is high. The medical community is working diligently to educate itself about this threat. This seems to be the best that we can do at the moment. There are no sensible special precautions that I can advise.

Q: My wife and I are concerned because, although we live in Seattle, we receive a lot of "junk" mail from agencies in Washington, D.C., Virginia, etc. What are the chances anthrax spores picked up in some D.C. mail-sorting facility can make it all the way out to our mailbox in Shoreline, intact? Should we be worried? What special precautions can we take to protect our family?

— David Cooper, Shoreline

A: Spores are dormant "hibernating" forms of the anthrax organism that are resistant to many conditions that would kill the growing form of the bacteria. Anthrax spores can survive for decades so that transport across country by mail should not be a problem for them. On the other hand, spores on the outside of a piece of mail are likely to get brushed off and diluted during transit and handling.

Laboratory experiments suggest that many thousands of spores must be inhaled to cause inhalation disease. My bottom line is that inhalation disease is very unlikely by the route you suggest. Skin anthrax is a bit more probable but still very unlikely.

If you are unhappy with this recommendation, you could consider using disposable rubber gloves to open and discard the envelopes in your mail.

Approximately 20 billion pieces of mail have been delivered since anthrax was detected in postal facilities. At the moment I would suggest that no special precautions are necessary for opening "familiar" parcels of mail.

• The Seattle-King County Health Department has been making considerable effort to educate physicians and the public about facts, educated guesses and prudent behaviors in response to bioterror issues. Their Web site contains information useful to both health-care professionals and the general public. The Web address is www.metrokc.gov/health/bioterrorism/. I consider this to be a balanced and reliable source of information.

Another useful Web site is maintained by the Washington State Health Department at www.doh.wa.gov/bioterr/.

To send a question to Dr. Henry Rosen, e-mail it to askthedoctor@seattletimes.com, or call 206-464-3338. Please include your name, city of residence and telephone contact number.