This electron micrograph image, which has been artificially colorized, shows monkeypox virus particles, in orange, purified from a cell culture at the National Institute of Allergy and Infections Disease's Integrated Research Facility in Fort Detrick, Maryland. (Provided by NIAID)

Two presumptive cases of monkeypox have been identified in Colorado, the state Department of Public Health and Environment announced this week.

The first infection, announced Thursday, occurred in a Denver-area man who had recently traveled from Canada, where there is an ongoing outbreak of the virus. Health officials are working to identify and monitor close contacts of the man’s, but Dr. Rachel Herlihy, the state epidemiologist, said there is not believed to be a high risk of community transmission.

The second infection, announced Friday, was in a person who was “a close contact of a person known to public health as a presumptive case of monkeypox,” according to a CDPHE news release. It’s not clear if the first and second cases are connected.

“Risk to Coloradans is low,” Herlihy said.

The cases are the first case sof monkeypox, which causes a painful rash and can be fatal, identified in Colorado in decades. Monkeypox is endemic in parts of central and western Africa, and rarely seen outside of those regions. Global health officials are still trying to understand what has caused the wider outbreaks in North America and several European nations.

The Colorado man who first tested positive in a sample analyzed locally, but the state must wait for official confirmation of the infection from the federal Centers for Disease Control and Prevention. So far, the CDC has confirmed nine cases of monkeypox in seven states.

Herlihy said the man flew to Colorado from Canada, but investigators are still working to piece together the timeline of when the travel occurred and when the man began showing symptoms.

“At this point we don’t believe the risk of transmission through travel would have been high risk,” she said.

The disease can have an incubation period of one to two weeks and typically first presents with fever, headache, muscle aches, swollen lymph nodes and exhaustion. One to three days later comes the telltale rash, often beginning on the face and spreading to other parts of the body. The disease can be fatal in roughly 3% to 6% of cases, though it is possible the strain currently circulating is milder. More severe cases typically occur in children and those with weakened immune systems.

Monkeypox is far less contagious than a disease like COVID-19. Herlihy said it can spread through skin-to-skin contact or contact with fluids from open rash lesions. It can also spread through large respiratory droplets. But, unlike COVID, transmission via the droplets typically requires especially prolonged contact.

Herlihy said the first Colorado case was identified after the man sought medical treatment. CDPHE had previously advised doctors to be on the lookout for potential cases of monkeypox.

Currently, monkeypox infections in the United States are spreading through two specific groups of people — those who have traveled recently to a place where there are active monkeypox outbreaks and men who have sex with men. The Denver-area man fits both categories, CDPHE said. But health officials caution that anyone who is exposed to someone with an infection can potentially catch monkeypox. People who show symptoms should contact their doctor.

The Denver-area man, described as a young adult, who first tested positive for the disease is currently isolating at home and his symptoms are improving, Herlihy said.

The second person in Colorado to test positive for monkeypox is “a young adult male who sought care in the Denver area and is improving and isolating at home.”

Colorado has ordered a supply of vaccine that can prevent monkeypox — and is also believed to lessen the severity of the disease when given to people after exposure. It is possible the vaccine could be given to the man’s close contacts in Colorado, but Herlihy said the state is still working to gather details on their potential exposures.

UPDATE: This story was updated at 5:14 p.m. on Friday, May 27, 2022, to reflect that a second Colorado man has tested positive for monkeypox.

John Ingold is a co-founder of The Colorado Sun and a reporter currently specializing in health care coverage. Born and raised in Colorado Springs, John spent 18 years working at The Denver Post. Prior to that, he held internships at...