Is the new COVID variant, JN.1, too smart for home tests? Here’s what science has to say

Anecdotal chatter in Fort worth underscore the premise that the latest COVID-19 variant, JN.1, is too wily for home test kits to detect. However, the science may be a bit more complicated.

Reasons why many are having to test multiple times to find out if they have the virus include testing too soon after exposure and the differences in how well the virus can replicate itself in one person compared to another, according to the New Jersey COVID-19 Information Hub.

“It’s not quite unusual, the virus that causes COVID-19, SARS-CoV-2 continues to evolve as more and more people become infected, and the virus makes copies of itself. It mutates, it changes, it gets better at evading our immune systems and making people sick,” Jessica Malaty Rivera, infectious disease epidemiologist at De Beaumont Foundation, told pbs.org earlier this month.

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When Star-Telegram visual journalist Steve Wilson started feeling under the weather a week ago, he heard from a friend who told him that he, too, was not feeling well. They both took a COVID home test. Wilson’s test came back negative and his friend’s was positive.

“Feeling we both got exposed together, I decided to re-test,” Wilson said.

The subsequent test came back positive.

Around the same time, Wilson said his wife started feeling unwell. “So, we tested her, and it was negative,” he said.

Wilson said we tested her again — negative — and then a third time came out positive.

“I don’t know if the current variant is harder for the test to detect or if people should take more than one test if they keep feeling bad,” he said. “I only did it because even though I tested negative, my friend tested positive, and we were together a couple of days before we got sick.”

When COVID variant JN.1 became the predominant infection

As recently as last fall, COVID hospitalizations and deaths in Texas continued to spike, Although the numbers haven’t topped previous peaks, many in the state are getting sick and dying from the virus. The COVID BA.2.86 variant had the acute attention of scientists at the time.

By December 2023, the new JN.1 variant was projected to account for 39%-50% of circulating variants in the United States, according to the Center of Disease Control and Prevention tracking.

“The proportion of JN.1 continues to increase more rapidly than other variants,” the CDC said. “Based on laboratory data, existing vaccines, tests, and treatments work against JN.1.”

JN.1 is causing an increasing share of infections and is now the most widely circulating variant in the United States. The spread of JN.1, however, does not seem to pose additional risks to public health beyond that of other recent variants, the CDC says.

Why home test kits may miss a JN.1 variant infection

The latest variant may take more time before showing a positive result with home test kits, according to the WebMD website.

“Some infectious disease doctors and patients have reported that tests taken days after symptoms appear turn up negative, then a couple of days later are positive,” according to the consumer-oriented health website.

Occurrences of false negative test results may have contributed to the skepticism over the efficacy of COVID home test kits.

But before you blame the test kits, or that perhaps the latest variant has gotten too smart, infectious disease experts offer answers. First, as the virus evolves so has our immune system — learning how to suppress the infection. Second, the mutation of the new variant does not load up as much of the virus at the moment of infection, according to a recent study. It may take up to four days from the moment of exposure before there is enough of a virus load in your system for a test to detect.

So, be aware of how COVID has evolved in the new variant when you test from home.

“Care must be taken in interpreting RT-PCR tests for SARS-CoV-2 infection — particularly early in the course of infection — when using these results as a basis for removing precautions intended to prevent onward transmission,” according to the National Library of Medicine.