The Colorado Department of Public Health and Environment announced Monday it will add 822 cases of novel coronavirus that meet national standard criteria of second infections to its COVID-19 data dashboard. 

According to a news release, the cases were reported between Aug. 20, 2020, and Feb. 28 of this year and represent 0.19% of Colorado’s case total. The median age among these second infections is 42 years old, and are scattered among 45 of the state’s 64 counties. 

“While reinfection is rare, it’s not unexpected based on what we know from similar viruses,” says the release. “Coloradans should continue to protect themselves, whether or not they have already had COVID-19, by following public health protocols – hand washing, mask wearing, physical distancing, and avoiding gatherings.”

The CDC defines a second infection as a second positive molecular amplification test 90 days or more after the first positive test, says the news release. The criteria also include infections that are genetically different from each other, to distinguish second infections from one continuous infection with intermittent virus “shedding.”

However, it is difficult to definitively tell the difference between those situations, and the state lab has been unable to sequence most of the cases it is adding to the dashboard, states the release, because most labs don’t keep samples for more than a few days. Other factors that make the sequencing difficult include reduced quality of specimens if they are stored for long periods of time and frequently lower amounts of virus present in second infections.

The release says the CDPHE’s State Public Health Laboratory has successfully sequenced seven pairs of samples that are of good enough quality to make accurate determinations about reinfection. Five of the pairs were genetically different, says the release.

“It’s important to note that the criteria used to define a new case or reinfection may change as we learn more about how long immunity lasts,” states the release.

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