A 13-year-old girl who thought she wasn’t infected with COVID-19 caused a superspreader event, family-style. According to a recent report from the CDC, it allowed the coronavirus to spread across four states.
The girl was believed to have been infected in June, exposed during a large outbreak. As a precaution, she got a rapid antigen test before going on her family vacation. She tested negative, but unfortunately, the result was false. On the day her immediate family embarked for the larger familial meetup, she started experiencing mild symptoms. She shared a house with 14 family members for eight to 25 days, and 11 of those people came down with COVID-19.
“The findings in this report highlight the need for those potentially exposed to COVID-19 to self-quarantine for 14 days after exposure or after interstate travel when mandated by state, territorial, tribal or local authorities,” the CDC said in a statement to TODAY. “Social distancing, mask use, and hand hygiene reduce transmission in group settings and might have prevented this outbreak had they been used.”
Problems with Rapid Antigen Tests
Not all tests for COVID-19 are created equal. And the different types of tests should be used in very different ways.
The most common test, a PCR test, is very sensitive. It’s also more invasive, and requires anywhere from one to four days to receive results from a lab. Its sensitivity means that there’s far less chance of a false negative result, but a positive result might not necessarily mean contagion.
A rapid antigen test, like the girl received, is less invasive and garners “rapid” results, often within 30 minutes. However, it’s far less sensitive. In a recent Harvard Health blog article, rapid tests were found to have a large percentage of false negatives.
“The reported rate of false negative results is as high as 50%, which is why antigen tests are not favored by the FDA as a single test for active infection,” Harvard reported.
The esteemed journal Nature agrees. “Antigen tests give results in less than 30 minutes, don’t have to be processed in a lab and are cheap to produce. Yet that speed comes with a cost in sensitivity. Whereas a typical PCR test can detect a single molecule of RNA in a microlitre of solution, antigen tests need a sample to contain thousands — probably tens of thousands — of virus particles per microlitre to produce a positive result. So, if a person has low amounts of virus in their body, the test might give a false-negative result.”
This sensitivity “cost” means that rapid antigen tests are not one offs; they need to be performed repeatedly to be truly useful in measuring viral load and infectiousness. The girl’s negative results meant that she wasn’t contagious at the time of the test, but she still had the virus. By the time she was sharing a house with her extended family, she was highly contagious.
Fortunately, all the family members have recovered.
Teens Carry The Virus, So Test Appropriately
While older adults and those with medical vulnerabilities are more at risk from COVID 19, teens and children contract and spread the virus to them very efficiently. They often show few or mild symptoms, but can carry large viral loads. The CDC also reported that teens, rather than kids, were almost twice as likely to be diagnosed with the virus.
If your teen or child has been exposed to the virus, they should get a PCR test, which is more sensitive to lower viral loads. And, of course, after any suspected exposure, a 14-day quarantine is paramount. The WHO and the CDC have also advised getting a PCR test if people showing symptoms test negative with a rapid antigen test.
13 year old spreads COVID to family, editor’s note: Images are used for illustrative purposes only.