Public Health Madison & Dane County reported 150 “suspected” cases of reinfection in Dane County on Thursday — a drastic increase from earlier estimates.
Dane County totaled only four cases of reinfection last week due to an error in how the department calculates cases. The “documented” cases that the PHMDC reported had also not been confirmed, according to guidelines set by the Centers for Disease Control and Prevention.
“Suspect reinfection means that a person had a positive test 90 or more days after a previous positive test,” said Health Education Coordinator Christy Vogt. “To confirm that this was a true reinfection, we would need sequencing on a sample from their first test and their later test, which is really hard to come by.”
The CDC’s “gold-standard” for confirming COVID-19 reinfection requires documentation of both initial infection and virus detection, with genetic sequencing data of the samples to support “a conclusion of high probability that reinfection has occurred.”
However, lab samples are not typically saved, so differentiating a ‘suspect’ reinfection from a ‘true’ reinfection now poses a challenge to the department. Due to this lack of data, PHMDC has no official, documented cases of reinfection on record.
“We don’t ask at our testing sites whether someone has been previously infected — and I don’t think this is standard practice at other test sites either,” said Kat Grande, a data team lead.
Grande pointed out that with ‘suspected’ reinfections, the PHMDC is presented with the question of whether or not the tests will register traces of the virus remaining from the first infection, causing inaccurate results. False positives also remain a concern.
“One way to answer this is to look at whether someone had negative tests in between the two positive tests that are separated by over 90 days,” she stated. “Unfortunately, we often don’t see that level of repeat testing.”