Is it COVID-19 or is it Lyme Disease?

MILFORD, Mass. — Fever, chills, muscle and joint pain — the natural diagnostic conclusion, these days, would be COVID-19. But that could be a mistake.

“This period in late June we’re in the very highest risk period every year for tick-related infections,” said Paul Sax, MD, Clinical Director of the Division of Infectious Diseases at Brigham and Women’s Hospital. “Now it doesn’t mean that it goes away after this point — it’s obviously high incidence year-round here in New England.”

The danger for Lyme Disease is highest in May and June because that’s when Blacklegged Tick nymphs are most active.

“The nymphal stage, these tiny, poppy-seed ones that are most risky, come out in mid-May and they usually last — depending on how dry the summer is — well into June,” said Thomas Mather, PhD, a professor in the Department of Plant Sciences and Entomology at the University of Rhode Island. “Then they will be pretty uncommon as you get later into July.”

Mather, also known as ‘The Tick Guy’ for his expertise in the field, said the nymphs are subject to desiccation — that is, drying out — as temperatures climb through August. Come fall, he said, the adult ticks emerge — and the risk of disease increases.

While several things distinguish Lyme Disease from COVID-19, the two infections actually cause similar symptoms.

“Fever, aches and fatigue — those are definitely things that could be seen with pretty much any infection,” Sax said.

But Lyme Disease and the current variant of COVID-19 share more specific symptoms, too — including chills, headache and even night sweats.

“There are a lot of things that can cause all these vague-ish symptoms,” Mather said. “And you know with Covid present that just adds one more fairly likely prospect.. But tick-borne diseases are in our lives, on our landscape and we need to keep them in mind, as well.”

Of course, both COVID-19 and Lyme Disease can be detected through testing. But lately, COVID-19 tests are proving unreliable at picking up infections early — even in symptomatic patients.

“The current theory on why people aren’t testing positive right away — the population is so heavily immune to COVID-19 because of previous exposures, vaccination or both that their immune system is reacting to the virus in an augmented way,” said Sax. “And causing these symptoms before the virus has a chance to kick in to its high-grade replication.”

That high replication is what allows for detection by antigen and PCR tests — and Sax said that recently, positive COVID-19 tests haven’t been showing up on symptomatic patients for up to five days.

While COVID-19 and Lyme share several symptoms — there is a sharp point of divergence: respiratory symptoms.

“Runny nose, congestion, sore throat, cough,” Sax said “Those are respiratory symptoms and it’s very uncommon, I would say almost unheard of, for Lyme to cause any of those.”

On the other hand, Lyme Disease often — but not always — produces a tell-tale rash at the tick-bite site. That rash may or may not take on a ‘bulls-eye’ appearance, said Sax. The problem is even if the rash is present, it can be hard to find — as ticks will bite in invisible places, such as the back of the knee or the back of the armpit.

“There are plenty of cases of Lyme that occur where people don’t recall the tick bite and have never seen a rash,” Sax said.

And that’s where Lyme Disease testing can be crucial.

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