There are three stages of Lyme disease to be aware of as Justin Timberlake becomes the latest star to confirm their diagnosis.
The 'Cry Me A River' singer took to Instagram to share a health update on Thursday (July 31).
Timberlake has been touring the world for the past 24 months, all while facing the reality of being diagnosed with the bacterial infection.
Mayo Clinic says the illness is caused by borrelia bacteria, which humans can contract it after being bitten by a tick.
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Its early symptoms can easily be dismissed as general illness, but if left untreated, it can become more severe over time.
Timberlake said, in part, on social media: "If you’ve experienced this disease or know someone who has - then you’re aware: living with this can be relentlessly debilitating, both mentally and physically.
"When I first got the diagnosis I was shocked for sure. But, at least I could understand why I would be onstage and in a massive amount of nerve pain or, just feeling crazy fatigue or sickness."
He added: "I was faced with a personal decision. Stop touring? Or, keep going and figure it out. I decided the joy that performing brings me far outweighs the fleeting stress my body was feeling. I’m so glad I kept going."
He's become the latest Hollywood star to speak out about the disease, which impacts around 480,000 Americans each year.
Here are its three main stages, explained.
Three stages of Lyme disease explained
Lyme disease is contracted via ticks, so the first obvious symptom could possibly be a tick bite, Mayo Clinic explains.
This might present as a 'tiny, itchy bump on your skin, much like a mosquito bite'. However, a tick bite alone doesn't always signal the disease.
Stage 1 Lyme disease
Within three to 30 days of an infected tick bite, you might experience symptoms including a fever, headache and extreme tiredness.
People may notice joint stiffness, muscle aches and pains and swollen lymph nodes.
A rash is another usual sign, although it doesn't always show up.
"The rash is usually a single circle that slowly spreads from the site of the tick bite. It may become clear in the center and look like a target or bulls-eye," Mayo Clinic explains, adding that it's usually neither painful nor itchy, but warm to the touch.
The rash often feels warm to the touch, but it's usually not painful or itchy.
Stage 2 Lyme disease
The next set of symptoms - which are 'more serious and widespread' - show up between three to 10 weeks after a tick bite.
These can include rashes on other parts of the body, neck pain or stiffness and muscle weakness on one or both sides of the face.
Pain in the back and hips that spreads to the legs, numbness in the hands or feet and painful, swollen eyes or eyelids are also reported.
The most serious of all is immune-system activity affecting both the eyes and heart.
Affected eye nerves could cause pain or vision loss, while affected heart tissue can result in irregular heartbeats.
Stage 3 Lyme disease
People with stage three Lyme disease can experience symptoms from both earlier stages, as well as more serious issues.
These stage three symptoms usually show up anywhere from two to 12 months after a tick bite.
In the US, the most common issue at this stage is arthritis, especially in big joints like the knees. People might experience pain, swelling or stiffness that sticks around for a while - or it might come and go.
If you have any concerns, then contact your doctor immediately.
Topics: Health, Justin Timberlake, US News, Celebrity
Ellie Kemp