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Colorado health officials reported a second case of measles in Mesa County on Monday, deepening concern about possible silent transmission of the virus in the county.
The new case involves an adult of unknown vaccination status, and it brings the total number of measles infections this year in Colorado residents to 21. That's more than three times above the number of infections reported in the prior decade.
What makes the new case especially worrying is that it is not clear where the person may have been infected, raising the possibility that there may be at least some silent transmission of the virus in the Grand Junction area.
That possibility was first raised by a case reported in Mesa County last week, in an unvaccinated person who had not recently traveled outside the area and who had no obvious contact with anyone known to be infected.
In a news release Monday, officials from the Colorado Department of Public Health and Environment and Mesa County Public Health said the two Grand Junction cases "may have had a common exposure" but did not provide more detail.
"Both were likely infected by a separate, unknown case," Hope Shuler, a CDPHE spokesperson, wrote in an email. "These cases had symptoms starting at about the same time so one did not infect the other. It is more likely that they both were exposed to a common, unknown case in the last few weeks."
In addition, state and Denver health officials announced Monday that passengers on the C concourse at Denver International Airport may have been exposed to measles Tuesday, Aug. 12, by an out-of-state traveler on a layover.
"This incident serves as a reminder that travel in crowded public spaces, such as airports, increases the risk of exposure to various communicable diseases," Dr. Rachel Herlihy, CDPHE's deputy chief medical officer, said in a statement. "It is important for everyone to stay up to date on their vaccinations, especially before traveling, to protect themselves and others."
As part of the announcement of both new incidents, health officials released a list of places and times where people may have been exposed.
Those who were potentially exposed should monitor themselves for symptoms of measles -- fever, cough, runny nose, red eyes and, later, a rash -- through the specified dates. If symptoms develop, people should call their doctor or local clinic prior to going in for treatment so that medical providers can take appropriate precautions against spreading infection.
The announcements of new cases and exposures in Colorado came as health officials in Texas declared the measles outbreak in their state to be over. Texas had been the epicenter of measles infections in the United States this year and also the source -- either directly or indirectly -- of infections that spread across the country.
But some Colorado residents have also been stricken this year with infections linked to international travel and outbreaks in other countries that are not believed to be connected to the Texas outbreak.
Colorado is maintaining a website of all the places where people may have recently been exposed to measles, as well as providing information on how to look up your immunization record.
So far this year, 14 of the 21 measles infections in Colorado have been in people who are unvaccinated or whose vaccination status is unknown. There have been five hospitalizations due to measles and no deaths.