By Emma Hitt, PhD

ATLANTA (Reuters Health) – A panel of experts assembled by the US Centers for Disease Control and Prevention, including US Surgeon General Dr. David Satcher, on Thursday conducted a telephone briefing on how office-based physicians should diagnose and treat inhalation anthrax.

Dr. Virginia Caine, with the Division of Infectious Diseases, Indiana University School of Medicine, stressed that physicians cannot afford to miss diagnosing inhalational anthrax, because the time from onset of symptoms to death can be as short as 3 days.

"The early signs are very similar to influenza, but a key sign can be a white mediastinum, lymphadenopathy, and pleural effusion," she said. She pointed out that rhinitis may often not be present, the white blood cell count is not necessarily elevated, and not all patients will have a fever.
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After initial flu-like symptoms, patients will feel better, but then enter a second phase, characterized by shortness of breath and chest tightness, Dr. Caine explained. "About 50% complain of acute abdominal pain and 5% have a usually fatal hemorrhagic meningitis," she said.

According to a CDC report in the November 1st issue of Morbidity and Mortality Weekly Report, a physician who suspects inhalational anthrax should determine whether the patient has had 2 to 5 days of flu-like symptoms. If so, the physician should obtain a white blood cell count, chest radiograph, and blood cultures, along with computerized tomography if the radiograph is abnormal. Rapid diagnostic testing for influenza may also be considered.

If results on any of the tests are abnormal, or if the patient is moderately or severely ill, the physician should start antimicrobial prophylaxis. A mildly ill patient should be observed closely for development of new symptoms, and antimicrobial prophylaxis should be considered.

According to the CDC, if pleural effusion is present, the physician should "obtain fluid for gram stain and culture, polymerase reaction, and cell block for immunohistochemistry." The physician should perform lumbar puncture if there are meningeal signs or altered mental status.

Dr. Caine's recommendation was less circumspect. She said that if suspicions arise that a patient does have anthrax, "go ahead and treat–don't wait." She also stressed that spores can sometimes lie dormant in the lungs for several days. "People have to take antibiotics for the entire 60 days," she said.

Among the antibiotics recommended for treatment of inhalational anthrax are ciprofloxacin, doxycycline and penicillin G procaine, although doxycycline is contraindicated in disease involving the central nervous system, according to Dr. Caine.

On Tuesday, the FDA provided specific antibiotic dosage recommendations for treatment of inhalational anthrax (post-exposure) in adults and children. The notice can be found on the agency's Web site at http://www.fda.gov/OHRMS/DOCKETS/98fr/cd01156.pdf.

"Amoxicillin for 80 mg/kg/day in three doses should be used for young children and pregnant women," Dr. Caine said. But she emphasized that physicians should use multiple antibiotic therapy. "Monotherapy is not recommended for treatment of any forms of anthrax except mild cutaneous anthrax."

"The CDC has a stockpile of antibiotics and very well-trained epidemiologists all over the US to respond to this problem," Dr. Satcher said. "But we are dependent on physicians to identify early cases of anthrax."