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The World Health Organization defines zoonotic infections as those diseases and infections that are naturally transmitted between vertebrate animals and humans. This broad class of diseases includes >200 specific diseases and syndromes covering an extremely variable range of clinical syndromes and medical therapy.1 Zoonotic infections can be transmitted to humans by direct contact with an infected animal or infected animal product, by ingestion of contaminated water or food products, by inhalation, and through arthropod vectors.

In North America, >4 million people are estimated to be infected annually. Zoonotic infections represent a significant public health problem in underdeveloped regions dependent economically on agricultural animals. The growth and mobility of the world’s population has resulted in the appearance of new zoonotic infections and the reemergence of previously eliminated ones. More than 50% of the newly identified infectious agents since 1976 are associated with animals.This diversity of presentation, human mobility, and zoonotic reemergence make the diagnosis and management of zoonotic infections a challenge for emergency physicians.

A zoonotic infection should be considered part of the differential diagnosis of any undifferentiated infectious syndrome: fever, headache, myalgias, malaise, and weakness. However, diagnosis is difficult. Determining risk factors for acquiring a zoonotic infection can help focus the differential diagnosis. Specific avocations and occupations that involve animal contact and certain medical comorbidities carry an increased risk (Table 155-1).Tick exposure carries a significant risk of zoonotic illness transmission, particularly of rickettsial disease. Also, the type of animal exposure is an important factor. Dressing, skinning, or handling an animal’s skin; a history of animal bite or scratch; and ingestion of animal or dairy products all carry an associated risk of zoonotic infection. Bush meat hunting is a particularly high-risk exposure activity. Recent travel, particularly in spring, summer, and early fall months, and history of habitation, particularly in an underdeveloped country or rural area, are additional risk factors. Zoonoses can occur at any time of the year, but in the U.S., most zoonoses show an increased incidence in the spring and summer.

Table 155-1 Risk Factors for Zoonotic Infection

Zoonoses that can present as an undifferentiated febrile illness or sepsis are listed in Table 155-2. The table lists only some of the more common zoonotic ...

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