The main source of infection in the country is sheep, followed by cattle and pigs. Herdsmen receive lambas as the main route of infection, and veterinarians are also highly susceptible to infection in the delivery of sick animals. In addition, peeling cattle and sheep, cutting wool, milking, cutting viral meat, slaughtering sick animals, children playing with sheep, etc. can be infected, germs from the contact of the broken skin into the human body. Laboratory staff can often infect bacteria from the skin and mucous membranes. When eating raw milk, dairy products and unboiled boiled animal meat, the bacteria can enter the body from the digestive tract.
In addition, germs can also be infected through the respiratory mucosa, eye conjunctiva and sexual organ mucosa. Clinical performance: the clinical performance of the disease is varied, in the case of individual patients, its clinical performance can be very simple, only as a local abscess, or complex and manifested as several organs and systems at the same time. Sheep and pig-type brucellosis are mostly heavier, the symptoms of bovine type is lighter, some cases can not be fever. In China, sheep-type cloth disease is more common, the natural course of untreated people is 3 to 6 months (average 4 months), but can be only 1 month or more short. The course of the disease can generally be acute and chronic, the acute stage of the bovine type is not obvious. The incubation period is 7 to 60 days, usually 2 to 3 weeks, and a small number of patients become ill months or more after infection. Most of the infected people in the laboratory became ill within 10 to 50 days. Human brucellosis can be divided into subclinical infections, acute and subacute, chronic infections, limitations and recurrent infections.