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By Mayo Clinic staffCertain factors may put you at greater risk of plague:
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Location. Naturally occurring plague outbreaks are most common in rural areas and in urban areas characterized by overcrowding, poor sanitation and a high rat population. Outbreaks can happen at any time of year.
Plague is present on most continents other than Australia. The greatest number of human plague infections occurs in countries such as Madagascar, Tanzania and the Democratic Republic of Congo. However, the largest concentration of infected animals is in the United States — particularly in New Mexico, Arizona and Colorado — and in the former Soviet Union.
- Time of year. Most plague infections occur from May to October. During these months, infected rodents and fleas are most active and people are more often outside and exposed to them.
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Contact with certain animals. Rats, squirrels, rabbits and prairie dogs are common sources of infection. Domestic cats also may become infected by such animals and pose a transmission risk to humans.
The disease usually spreads through fleabites, but you can also contract plague after being exposed to an infected animal that may have coughed infectious droplets into the air or through a break in your skin after handling an animal with plague. Groups at increased risk include veterinarians, cat owners, hunters, campers and hikers in areas with recent plague outbreaks among animals.