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Clinical Signs Differ Between Inhalational Anthrax, Influenza

Kate Traynor

The 10 recent cases of inhalational anthrax that resulted from bioterrorist attacks are starting to reveal symptom profiles that may help clinicians distinguish anthrax from influenza and flu-like illnesses.

According to the Nov. 9 Morbidity and Mortality Weekly Report, 80 percent of the patients with inhalational anthrax had shortness of breath. In contrast, previous studies indicate that 6 percent of patients with laboratory-confirmed influenza or influenza-like illness reported this symptom.

Twelve percent of people with influenza or similar illnesses reported nausea or vomiting, compared with eight of the 10 patients with inhalational anthrax.

Although 64–84 percent of patients who contract influenza or flu-like illnesses have a sore throat, only 20 percent of the patients with anthrax had this symptom. And a runny nose, which is observed in about 70–80 percent of patients with influenza or similar illnesses, was seen in only one of the 10 patients with inhalational anthrax.

Half of the patients with inhalational anthrax reported having a headache, and half had muscle pain. In contrast, about 75–90 percent of patients with influenza and influenza-like illnesses reported headaches, and about 65–95 percent had muscle pain.

All 10 cases of inhalational anthrax have been characterized by fatigue, malaise, and fever or chills—symptoms that are also strongly associated with influenza and influenza-like illness. Each patient with inhalational anthrax had an abnormal chest radiograph, a finding not normally associated with influenza unless the patient is also young, elderly, or has a chronic lung disease.

An elevated temperature and a slight or unproductive cough occur about as often in patients with inhalational anthrax as in patients with influenza or influenza-like illness.