Infections That Cause Headaches and a Fever

Headaches are common and usually nothing to worry about. But if you have a fever, in addition to a headache, please see your health care provider for a proper diagnosis. The combination of a fever and a headache may be a sign of a serious infection.

A headache and fever may be a sign of an infection that is localized to your brain and/or spinal cord, which forms your central nervous system. Specific examples of central nervous system infections include meningitis, encephalitis, or brain abscess.

Systemic or whole body infections, such as the flu or early HIV symptoms, may also cause a headache and fever, as can less common conditions like a bleed or a tumor in the brain.

This all being said, sometimes a headache and fever are signs of a run-of-the-mill viral infection that simply needs to run its course.

Here we will explore both infectious and non-infectious causes of a headache and fever.

As an aside, it's important to note that while knowledge can be empowering, it can be tricky and subtle distinguishing what is serious and what is not—so be sure to get your headache and fever checked out by a doctor.

In addition to a severe, generalized headache and a high fever, symptoms of meningitis may include neck stiffness, nausea, vomiting, confusion, rash, and/or a sensitivity to light. That being said, a person typically will not have all of these symptoms, and that is why a doctor’s examination is critical.

Other potential symptoms of meningitis include rash, joint pains, seizures, or other neurological deficits.

In order to make the diagnosis, a person with suspected meningitis will undergo a lumbar puncture, also known as a spinal tap. During a lumbar puncture, the cerebrospinal fluid (CSF) is analyzed to determine whether an infection is present and if so, what type of infection.

In addition, a person with suspected meningitis will also usually undergo laboratory studies, including blood cultures and a white blood cell count (white blood cells are infection-fighting cells in the body). A treatment plan will usually follow. There is also a popular meningitis vaccine for prevention.

Encephalitis is an infection of the central nervous system that may be caused by a virus, bacteria, or fungus.

Encephalitis is similar to meningitis, but a key difference is that encephalitis causes people to have abnormalities in brain function.

This means that a person will have an impaired mental status or have movement or sensory problems, even paralysis (whereas this is generally not the case in meningitis). Because the two can be so difficult to differentiate, doctors sometimes use the term “meningoencephalitis.”

A brain abscess is a rare, but potentially life-threatening condition, in which infected fluid collects in the brain. Symptoms of a brain abscess can resemble that of meningitis or encephalitis and include: fever, headache, neck stiffness, neurological dysfunction, and confusion. A headache from a brain abscess and the confusion occur as a result of the elevated intracranial pressure that the infected fluid collection causes on the brain, as it continues to grow and take up space.

Diagnosis of a brain abscess is confirmed with a CT scan of the brain, which classically shows a ring-enhancing lesion. Patients are treated with antibiotics given through the vein and sometimes surgical drainage of the abscess. Clearing of the infection is documented, usually through serial CT scans, and can take weeks to months.

A sinus headache and fever, in addition to a variety of other possible symptoms, like facial tenderness or swelling, ear pain, tooth pain, and thick nasal discharge may indicate a bacterial sinus infection. The good news is that if you have bacterial sinusitis, a week or so of antibiotics, rest, fluids, and steam should clear it up quickly.

Very rarely sinus infections lead to other complications like a brain abscess, meningitis, blood clot, or osteomyelitis—an infection of the facial bones (especially the forehead). If you are diagnosed with a sinus infection, be sure to follow up with your healthcare provider if your fever persists while taking antibiotics. 

A systemic or whole body infection, such as influenza, commonly known as “the flu,” or infectious mononucleosis, often referred to as “kissing disease,” or mono, can cause fever and headache, as can a number of other systemic infections like HIV or AIDS.

Usually, there are other clues that help doctors confirm a systemic infection. For example, if you have the flu, you will typically have body aches and a cough, in addition to a headache and fever. If you have mono, you will have a sore throat and test positive on the monospot test, a rapid test used to diagnose infectious mononucleosis.

Finally, it's important to understand that other symptoms besides fever can occur with a systemic infection, like weight loss, night sweats, and/or generalized fatigue or malaise.

Besides infections, other illnesses may cause a headache and fever and affect the whole body. These include a number of rheumatic diseases like:

• Systemic lupus erythematosus or lupus
• Sarcoidosis
• Giant cell arteritis

There are also rare, but very serious causes of a headache and fever like subarachnoid hemorrhage, pituitary apoplexy, or a brain tumor.

For example, a subarachnoid hemorrhage (which causes bleeding in the brain) may cause a thunderclap headache—an abrupt, severe headache "like a clap of thunder." Classically, the headache of a subarachnoid hemorrhage is sudden, explosive, one-sided, and associated with nausea, vomiting, mental status changes, and neck stiffness. Sometimes a fever can also occur.

Of course, there are medical conditions that mimic a thunderclap headache. That said, only a health care provider can make this determination after evaluating you and ordering necessary brain imaging.

While it may just be that you have a mild illness and need fluids and a fever-reducing medication for your headache and fever, it's important to be safe and get it evaluated by a doctor. Fever and headache can be a potentially serious combination, so err on the side of caution and get it checked out.