Feeling a little fatigued is normal after a long day at work, intense exercise or during stressful periods. But if you’re feeling exhausted and sluggish all day, every day, there’s a good chance that something else is going on with your health. Extreme fatigue is often a symptom of illness and is the tell-tale symptom of one viral infection, in particular.

Infectious mononucleosis, also referred to as mono or the kissing disease, is characterized by fatigue that doesn’t seem to let up, even after a month or two. Although mono is most common in teenagers and young adults in college, it can infect just about anyone at any age. And, once you’re a carrier, you have a dormant version of the virus forever.

If you notice that you’ve been feeling extra tired lately and have also noticed some other common symptoms such as a sore throat, mild fever, headaches or muscle stiffness, visit the doctor and get tested for mono. A diagnosis will give you the excuse you need to rest and let your body fight off the virus, rather than trying to push through and make your fatigue even worse.

Understanding mono

Mono is caused by a virus—usually the Epstein-Barr virus (EBV), which is part of the herpes family of viruses. The illness is called the “kissing disease” because it is commonly transmitted through saliva while kissing someone, but you can also spread it by sharing drinking glasses and utensils or through coughs and sneezes. However, it can take a few weeks for symptoms to appear after contracting the virus, because EBV has an incubation period of around 30 to 40 days.

Symptoms of mono may begin by feeling like a common cold. You may experience headaches, a mild fever and swollen lymph nodes. The fatigue mono causes is usually the tell-tale sign that your illness is something different from a cold.

Symptoms of mono vary from person to person but typically include:

• Fatigue
• Muscle stiffness
• Sore throat
• Headache
• Fever
• Swollen lymph nodes
• Swollen spleen and/or liver
• Rash with little red bumps
• Loss of appetite

Mono symptoms can last for a few weeks, but fatigue and swollen lymph nodes usually last the longest. The virus can cause enlargement in the spleen, and in extreme causes, cause the spleen to rupture. For this reason, people with mono may have to avoid playing sports or getting back into their normal, active routines for a few months to prevent the spleen from rupturing.

Once you have been infected with mono, the virus stays inside your body in a dormant state. Most people build up enough antibodies to never experience symptoms again, but some people may have an active infection and its symptoms repeatedly. It is actually believed that almost 90 percent of people in the world carry the virus that causes mono; however, not all of these people will experience symptoms of any kind.

The link between mono and fatigue

Symptoms like fevers and headaches caused by mono might last four to five weeks during the infection, but fatigue can last much longer. In some cases, you may still feel very fatigued two to three months after the infection has cleared.

This fatigue occurs because your body is so busy fighting the infection that you’re left with little energy for even the most basic daily tasks. Students often have to take weeks off of school to recover from mono.

The best way to cope with mono-related fatigue is to rest and give your immune system what it needs to continue fighting the infection. Do not try to push yourself too hard—this will likely burn you out and make your fatigue worse.

How to treat mono

There is no cure for mono. The virus will eventually clear up on its own and remain dormant. Because mono is viral, antibiotics don’t work well against it. The only things you can really do are rest, eat a healthy diet, boost your immune system and drink lots of water.

Fluids like water and juice can help soothe a sore throat, relieve fevers and keep you hydrated so your immune system can continue fighting the infection. Gargling with salt water can help relieve a sore throat, too.

A healthy diet will give your body the right vitamins and minerals it needs to stay strong. Probiotics may also help your body fight the infection. These healthy bacteria are linked to a strong immune system because they regulate the gut microbiome.

Additionally, you can try taking supplements for the lymphatic system to help ease your symptoms.

Slow down and relax

Often, people who get sick with mono try to push through their illness and make matters worse. If you are diagnosed, give yourself time to rest and recuperate so your body can more easily fight the infection and get you back on your feet as quickly as possible.