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AHRQ Study Identifies Key Symptoms Differentiating Inhaled Anthrax from Flu

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Press Release Date: September 1, 2003

Researchers have identified key symptoms that may help distinguish inhaled anthrax from the flu and other common respiratory conditions in the event of a bioterrorist attack, according to a new study partially funded by the Agency for Healthcare Research and Quality and published in the September 2, 2003, issue of Annals of Internal Medicine.

Results of the study are being used to create the first evidence-based pre-hospital screening protocol designed for response to future anthrax attacks. By helping emergency management and public health authorities rapidly and accurately identify both potential cases and likely non-cases, this protocol, once fully tested, will help to preserve scarce hospital capacity while ensuring that patients receive appropriate advanced medical care.

Combining data from the 11 inhaled anthrax cases from the 2001 attacks with historical case reports of 17 additional patients, researchers at Weill Medical College of Cornell University compared the features of anthrax-related illness with more than 4,000 cases of common viral respiratory tract infections such as the flu. While symptoms such as fever and cough did not reliably discriminate between anthrax and flu or flu-like illnesses, others—most notably neurologic problems like dizziness and confusion, serious gastrointestinal symptoms like nausea and vomiting, and shortness of breath—were much more common in patients with inhaled anthrax. Although sore throat and runny nose were present in some cases of anthrax infection, these flu-like symptoms never occurred without at least one of these other symptoms.

"The ability to differentiate between patients who should be tested—and triaged—to determine whether they have anthrax or are coming down with other illnesses is particularly important in the wake of a possible bioterrorism event," said Carolyn Clancy, M.D., director of AHRQ, which funded the study as part of its bioterrorism preparedness research portfolio. "This study provides the critical foundation needed to direct further science-based research in this important area."

Lead study author Nathaniel Hupert, M.D., an assistant professor of public health and medicine at Weill Medical College of Cornell University, agreed. "This highlights the importance of considering the complete clinical presentation of inhaled anthrax, as opposed to simply its component signs and symptoms, in formulating accurate screening protocols," he said. Four of the 11 patients who developed anthrax in 2001 were originally sent home with diagnoses of a viral syndrome, bronchitis, or gastroenteritis.

The study, "Accuracy of Screening for Inhaled Anthrax after a Bioterrorist Attack," is published in the September 2, 2003, issue of Annals of Internal Medicine.

For more information, please contact AHRQ Public Affairs: Farah Englert, (301) 427-1865 (


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