Fever means a temperature over 100.6° F. (38.0° C.). What we memorized about 98.6° is simply average, not “normal”. Some people have a normal temperature of 100°. However, since temperatures are always higher in the afternoon, 100° in the morning makes me worry a little. Also, I’m convinced there’s a fever if a patient has drenching sweats at night. “Drenching” means they can squeeze it out of their pajamas or sheets, nothing less.
The Common Cold sometimes begins with a fever on Day #1, with maybe a sore throat. But that fever goes away quickly, and a runny nose begins on Day #2 or #3. That’s when the cough may begin, or even later. That’s not what we’re talking about here — this section deals with significant cough plus significant fever both at the same time.
Covid-19 — We’ve noted how anyone with Covid symptoms needs a Covid Test; “cough” for under 10 days surely counts. If they’re not very sick, meaning no “true” shortness of breath (SOB — the standard medical abbreviation; click for a definition of “true”), and no chest pain with each breath, we probably tell them to isolate at home while the test is pending. If the test is negative but symptoms had just begun a few days ago, they need a repeat test.
The rest of this discussion assumes the patient does not have Covid-19.
If someone has both cough and fever, I immediately think of a virus like Influenza, or of Pneumonia. (which is caused by bacteria; click link for description of differences among Germs). Bacterial Sinusitis is also a possibility. Here we’re talking about someone who just became ill. Anyone with fever going on a week or more definitely has something more complicated, as we’ll note below.
Influenza (“The Flu”) — Flu season occurs between late November and April, though other viruses can cause the same type of illness any time of year. During Flu season, I immediately diagnose Influenza if the patient has the typical:
- Sudden onset fever
- Muscle aches all over
- Dry cough
- Lungs sound normal on exam
- Some fatigue perhaps, but no true SOB
The illness starts off strong, eases up on Day #3 or #4, and is virtually gone on Day #5. Any other course or time frame makes me question the diagnosis. If the illness occurs in Flu Season (late Nov. to late April), the diagnosis is clinched. At other times a year, we call it a “Viral Syndrome” or “Flu-Like Virus,” but are careful to be sure there’s no SOB. Respiratory tract viruses don’t cause true SOB, unless complications develop.
Chest X-Ray? It’s usually normal with a virus (maybe some minor, vague findings). But we don’t order x-rays on everyone with typical symptoms. Maybe on the elderly, certainly the immunocompromised, and patients with true SOB. We certainly get a Chest X-Ray if there’s still a fever on Day #4 that hasn’t begun to get even the least bit better.
Some clinical settings can test for Influenza with a nasal swab. If it’s positive, that’s what they got. If negative, it could be a false-negative (25% to 50% of tests), or another virus that acts the same.
Treatment for the Flu? There are special antiviral antibiotics that only work if begun within 48 hours; we’d give them to anyone who tests positive, but certainly to the elderly, pregnant women, or others with weak immune systems. We might give them if someone else in the house just had fever, aches, and cough during Flu Season. Otherwise, there are meds for muscle pain & fever, but the only real cure is time. A work or school excuse helps. But we don’t give regular antibiotics, which only treat bacteria, not viruses.
Someone with Influenza can get a “secondary Pneumonia” and suddenly get worse, aftere they were seemingly improving. That’s because Influenza weakens the immune system for a brief time, but long enough for bacteria to grow into Pneumonia. Such patients get treated as in the next paragraph.
Pneumonia — As opposed to uncomplicated Influenza, Pneumonia is more likely to kill. It implies bacteria in the lungs. And it always gives a fever, except in the very old or debilitated, and patients with very weak immune systems (especially those getting chemotherapy or other medicines that strongly interfere with our body’s defenses).
We diagnose Pneumonia by hearing crackles during inspiration (called “rales”) when listening to the lungs with a stethoscope. In children, fever plus rales is enough for the diagnosis. In adults, a same-day chest x-ray is best form.
Even if we don’t hear rales, we’d order an x-ray in patients with fever + cough who are at high risk of pneumonia:
- Elderly, Debilitated, or Immunocompromised
- Cough + Fever + True SOB
We also order an X-ray for any patient, rales or not, whose Cough + Fever haven’t begun to get even the least bit better by Day #4. If the x-ray is normal, we’d probably get a Chest CT Scan for the persistent fever.
A Chest X-Ray on an adult is excellent for finding any Pneumonia. If we see one, we treat it. So if the x-ray is normal, they have Acute Bronchitis (a virus, often the Flu). Some clinicians argue that it’s possible to have pneumonia with a normal chest x-ray. Maybe sometimes; maybe on the very first day of illness. But for all practical purposes, hardly ever.
It’s so easy to prescribe just antibiotics whenever there’s a fever and cough, & skip the x-ray. It can make sense in Pediatrics if we also hear rales in the lungs. Routinely prescribing antibiotics surely makes patients happy, and remain a customer of the practice. But it leads to horrible overuse of antibiotics, which generates antibiotic-resistant bacteria. Get one of those, & you won’t be so happy.
Sinusitis — Infection of the sinuses usually doesn’t cause a fever. If so, the fever would rarely begin on the first day of symptoms. We think about Sinusitis as a diagnosis for Cough + Fever if there’s pressure in the face, maybe congestion, especially on just one side. Tapping on the upper teeth causing bad pain in the same cheek is a clue for the maxillary sinus.
Diagnosis of Sinusitis is difficult, because sinus X-rays may be either false-negative or false-positive. A CT Scan is a better test in that sense, but is easily false-positive. One study squirted Rhinovirus, cause of the Common Cold, into volunteers’ noses, and a few days later performed sinus CT Scans. Many seemed to show Sinusitis, although they clearly only had a cold due to a virus.
The American Academy of Otolaryngology and also the Infectious Disease Society of America only recommend diagnosing Sinusitis as a cause of Fever if there are face and nose symptoms as mentioned above, and either:
- Has been going on at least 3 days from start of illness; OR
- Illness began as a simple cold, then suddenly got worse after 5-7 days, with new fever and worse facial pressure
I’m also much more willing to diagnose Sinusitis in immunocompromised patients (with other diseases that cause weak immune systems), because bad things can happen. Of course, anyone with facial symptoms of sinusitis who’s mentally confused, or has neurologic symptoms like major changes in vision, needs to go right to an ER for a CT Scan to rule out spread of infection to the brain or eye.
To Summarize — Acute Cough with a Fever is usually due to a virus, although that virus could be Covid-19 or Influenza, which require their own special management strategies. Still, we worry about bacterial Pneumonia when someone has a cough + fever, especially if they’re elderly, or have a serious underlying medical condition (immunocompromised). And whereas Sinusitis can cause a cough + fever, that’s not so common.
See also Acute Cough for the clinician’s condensed thought-process when face-to-face with a patient.