The death of a star high-school pitcher and quarterback in Northern Colorado has been attributed to a rare form of the plague, county officials say.

Taylor Gaes died June 8, a day after his 16th birthday, as he was being driven to a hospital. The cause of death, officials at the Larimer County Department of Health and Environment confirmed, was septicemic plague, a form in which the disease enters the bloodsteam directly.

Gaes is the first resident of the county to have died of the disease, which is extremely rare and lethal in humans, since 1999. “While the investigation is still ongoing, the individual may have contracted the disease from fleas on a dead rodent or other animal on the family acreage,” the Larimer County Department of Health and Environment said in a statement. It is coordinating the investigation, which it says includes experts from the U.S. Centers for Disease Control, the State Health Department, and the Larimer County coroner’s office.

Health officials asked that anyone who visited the family’s home or attended the scattering of his ashes on the family’s property before the cause of Gaes’ death was determined seek medical attention if they developed a fever. Plague “can spread through rodent populations in a localized area – often resulting in mass animal ‘die-offs,'” the health and environment department statement said. It cannot be passed from human to human. The Centers for Disease Control and Prevention report that an average of seven human plague cases are reported each year nationwide, with most in Northern New Mexico, northern Arizona, southern Colorado, California, southern Oregon and far western Nevada.

Katie O’Donnell, a spokesperson for the county health and environment department, told People and the Denver Post that Gaes had shown flu-like symptoms, with a fever and aches. He was forced to leave a Colorado Rockies game with his family June 7 because of the pain, but seemed better that night. At around 5:30 a.m. June 8, he awakened his parents to say that he had coughed up blood, according to Coloradoan.com. He died during the 20-mile drive to the hospital in Fort Collins.

Gaes was the starting first baseman and the No. 2 pitcher for Poudre High School in Fort Collins. “We often talk about Taylor’s potential as an athlete, but he was much more than that,” baseball coach Russell Haigh told the Denver Post. “He was a good friend to all of our players. He was a special young man.”

His family chose to have his name released because a few hundred people attended a ceremony at their rural Cherokee Park property outside Fort Collins. “They would hate to see people get sick from it,” O’Donnell told the Denver Post. “There’s a very slim chance that anyone would.”

His family has created the Taylor Gaes Memorial Baseball Fund to pay baseball league entrance fees for kids. “The belief that any kid should have the opportunity to play the game of baseball was a passion of his,” a statement on the site says. “He never understood why money should play a factor in a young person’s ability to experience the joys of the game.”

Here’s how different forms of plague (bubonic, septicemic and pneumonic) can be transmitted, from the CDC:

Flea bites. Plague bacteria are most often transmitted by the bite of an infected flea. During plague epizootics, many rodents die, causing hungry fleas to seek other sources of blood. People and animals that visit places where rodents have recently died from plague are at risk of being infected from flea bites. Dogs and cats may also bring plague-infected fleas into the home. Flea bite exposure may result in primary bubonic plague or septicemic plague.

Contact with contaminated fluid or tissue. Humans can become infected when handling tissue or body fluids of a plague-infected animal. For example, a hunter skinning a rabbit or other infected animal without using proper precautions could become infected with plague bacteria. This form of exposure most commonly results in bubonic plague or septicemic plague.

Infectious droplets. When a person has plague pneumonia, they may cough droplets containing the plague bacteria into air. If these bacteria-containing droplets are breathed in by another person they can cause pneumonic plague. Typically this requires direct and close contact with the person with pneumonic plague. Transmission of these droplets is the only way that plague can spread between people. This type of spread has not been documented in the United States since 1924, but still occurs with some frequency in developing countries.