Dead ground squirrels found in the family's woodpile were later determined to have had plague. But the doctor he saw twice didn't recognize the disease. Bubonic plague, which accounts for 80 percent of cases, is marked by swollen lymph glands, called buboes. It's harder to diagnose septicemic plague, which circulates in the bloodstream, and pneumonic plague, which infects the lungs and is particularly dangerous because it can be transmitted through coughing. Generally, those in contact with a pneumonic plague victim are also treated with antibiotics.
Most people become sick two to seven days after infection.
Other symptoms are fever, chills, headache, muscle pain, nausea, vomiting and diarrhea. The incidence of plague appears to be cyclical, apparently linked to the high-moisture, milder winters typical of El Nino years that cause rodents to thrive, Ettestad said. This year, the rodent population in New Mexico is estimated at 10 to 20 times higher than last year, when no one in the state caught plague. Believed to have evolved in central Asia, plague is new to the United States. It arrived about 1900 in San Francisco aboard trading ships from China and spread from urban rats into the wild rodent population of the West.