Bioterrorism preparedness
Evaluation and management of persons concerned about anthrax exposure
October 11, 2001
Awareness and concern regarding biological weapons, particularly anthrax, has increased in the community. The following information is intended to help health care providers evaluate and counsel persons regarding anthrax exposure and infection.
There is no evidence of anthrax or other unusual infectious disease activity occurring in King County. Persons who believe they are victims of a potential threat involving biological agents or that they have been intentionally exposed to a harmful biological substance should contact the local law enforcement agency (dial 911) to report the incident. When indicated, additional investigation and/or specific advice from Public Health regarding the need for further evaluation of the patient will follow. In the absence of confirmation of a likely anthrax exposure, patients should be reassured that the risk of anthrax is remote, and no antibiotic prophylaxis is recommended. Public Health strongly recommends against prescribing prophylactic antibiotics and/or purchasing gas masks in the absence of any surveillance or laboratory evidence of a bioterrorist event.
There are no useful tests to determine if persons are infected with anthrax before they become ill. Nasal swabs to detect anthrax spores have been used in investigations of known or presumed anthrax exposure as determined by law enforcement and public health authorities, but are not useful outside of that setting.
Nasal swabs and other tests that are obtained during investigations help determine how the organism was spread. These tests do not provide useful information about whether a specific individual needs treatment. Persons who have had a confirmed or likely exposure to anthrax as determined by law enforcement and/or public health authorities would be advised to take preventive antibiotics regardless of the results of laboratory screening tests.
In the absence of a known or suspected exposure to anthrax, persons presenting for clinical evaluation of "flu-like" illness should be managed as usual. The most critical aspect in making a diagnosis of anthrax is a high index of suspicion associated with compatible history of exposure. Inhalational anthrax begins after an incubation period of 1 to 6 days with nonspecific symptoms of malaise, fatigue, myalgia, and fever. There may be an associated nonproductive cough and mild chest discomfort. These symptoms usually persist for 2 or 3 days, and in some cases there may be a short period of improvement. This is followed by the sudden onset of increasing respiratory distress with dyspnea, stridor, cyanosis, increased chest pain, and diaphoresis. There may be associated edema of the chest and neck. Chest X-ray examination usually shows the characteristic widening of the mediastinum and, often, pleural effusions. Pneumonia is not typical of inhalation anthrax.
Early symptoms of anthrax are entirely nonspecific. However, (1) the development of respiratory distress in association with radiographic evidence of a widened mediastinum due to hemorrhagic mediastinitis, and (2) the presence of hemorrhagic pleural effusion or hemorrhagic meningitis should suggest the diagnosis. Sputum examination is not helpful in making the diagnosis, since pneumonia is not usually a feature of inhalational anthrax.
Public Health should be notified of unusual numbers of persons with febrile respiratory tract illness. During the winter "respiratory virus season", an increase in the number of persons with febrile respiratory tract illness is expected. Clinicians should use their best judgment to determine if an increase over the expected number of cases is occurring.
Any unusual cluster or manifestations of illness should be reported immediately to Public Health at 206-296-4774 during working hours and 206-726-2128 after hours.
For more information on anthrax visit our website: www.metrokc.gov/health/bioterrorism and see Inglesby TV, et al. Anthrax as a biological weapon: Medical and Public Health Management. JAMA 1999;281:1735-1745; available online at: http://jama.ama-assn.org.
