HONOLULU (KHON2) — The summer and fall spike of COVID-19 cases in Hawaii showed up in more than just the daily test numbers. A program that tracks the flu detected the biggest jump yet in samples that turned out to be COVID instead.

More than one-third of the samples of negative flu tests turned out to be COVID in recent weeks — the largest portion ever in the pandemic.

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According to State health data on flu tracking, none of 520 respiratory specimens in the latest weekly flu surveillance popped up positive for influenza — which means hundreds of people who thought they would come down with flu had something else.

Turns out more than 37% of those also screened for COVID were positive for that instead — 52 out of 138 samples re-tested for COVID as part of what’s called “sentinel surveillance,” within the flu program.

“It mirrors what we saw in the COVID testing: We saw an increase in the delta variant, a surge,” explained Thomas Lee, assistant professor of epidemiology at the University of Hawaii. “What that proves is that our influenza surveillance is doing its job.”

The flu surveillance program has also checked samples for COVID — just in case — for over one year. There has usually been a small and steady trickle of COVID detected, but the jump in the past two weeks is startling: More than 30% of the subset of negative flu sampled for COVID registered positive in the middle of August and more than 37% the following week — the most so far.

“A lot of times if you’re in a younger population or demographic, you may not seek to get COVID tested, especially knowing that you’re vaccinated,” Lee said. “However, if you’re at a doctor’s office for some other reason, and you’re part of the surveillance, then you’ll get picked up and then you’ll get tested for the different strains of the flu and also COVID.”

According to the CDC, both COVID and the flu have symptoms in common like fever or chills, cough, shortness of breath, fatigue and body aches.

“We do know that the loss of taste and smell is unique to COVID, but once again, if you’re fully vaccinated, the chances of you experiencing a lot of those severe symptoms are lessened to the extent that if you do get infected with COVID and are fully vaccinated, your symptoms are probably going to mirror those of the flu,” Lee said.

Whether these cases were vaccinated or not, tested at the same time for COVID or found out later, or are added into the overall case numbers later is unclear. KHON2 has asked the DOH for more details for weeks and is still waiting for DOH’s answers, but some fine print in the reports explained that patients in the sentinel surveillance batch have respiratory symptoms but are not hospitalized and have not traveled outside of Hawaii.

Doctors and public health experts said it is a good reminder to take action again both viruses — get the COVID vaccine and your annual flu shot.

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“Flu is kind of forgotten right now,” Lee said, “but we are carefully monitoring the potential impact of flu on top of COVID. “