The short answer is yes. Yes, you can have pneumonia without a fever.
I strongly recommend that you read the rest of the article for the long answer because it is a very important question and you need more information to understand the specific situations.
As a practicing MD, my patients and their families have asked this question many times. In the last 15 years, I have treated thousands of very sick patients hospitalized with pneumonia and many of them did not have a fever. I have put this article together to explain why it is important to understand when you can have pneumonia without a fever and what that means.
The presence of a fever with pneumonia doesn’t always mean you are more likely to have a worse outcome. The absence of a fever does not necessarily mean that your pneumonia is not serious. In fact, some research has suggested that the opposite may be true. You may actually have a worse outcome if you have pneumonia without a fever in certain specific situations.
The presence of a fever with pneumonia doesn’t always mean you are more likely to have a worse outcome. The absence of a fever does not necessarily mean that your pneumonia is not serious. In fact, some research has suggested that the opposite may be true. You may actually have a worse outcome if you have pneumonia without a fever in certain specific situations.
Why do some people have pneumonia without a fever, and others have one with a fever?
A fever is a type of immune reaction. It is one of the ways your body tries to fend off an invasion by disease-causing germs. Pneumonia is a type of infection where the invading germs settle down in your lungs. To have a fever with pneumonia, the following sequence of events must happen inside your body.
- Invading germs produce certain specific chemicals capable of triggering a fever.
- Your immune system recognizes those chemicals as signs of an invasion by disease-producing germs, and pulls the trigger to start a fever.
- Your immune system works to magnify the signal and produce the right chemical to send the signal to a specific part of the brain.
- The part of the brain that controls your body temperature resets your internal thermostat to produce a fever.
- The thermostat releases chemicals that affect your metabolism—an energy-consuming series of chemical reactions.
- Your body uses more energy to produce heat until you reach the temperature set by your brain’s thermostat
Any defect in the steps can result in pneumonia without a fever.
There are certain viruses that don’t produce fever-causing chemicals. There was a research article published in the Cambridge University Press where they identified such viruses. (A link to the research article is included in the reference section). Some people have defects in the immune system that causes it fail to recognize the specific triggers. Some people have defects in producing the signal-magnifying chemicals, and are unable to tell the brain to reset the thermostat to start a fever.
People who are at risk for having a worse outcome when suffering from pneumonia without a fever
People who have a defect in the 5th and 6th sequence of events are vulnerable to have pneumonia without a fever with a worse outcome.
There was an important research article published in the BMC Pulmonary Medicine Journal. They reviewed 1,834 patients hospitalized with pneumonia, and analyzed several factors to find out who did better and who did worse. One of the factors was the presence or absence of a fever. When they analyzed the data, it appeared that among hospitalized patients, those patients suffering from pneumonia without a fever seemed to have a worse outcome compared to pneumonia patients who had a fever.
Another medical review article analyzed the data from several clinical trials and patients diagnosed with sepsis and a fever and sepsis without a fever. These patients had several different types of infections, but all of them had sepsis. If you want to learn more about sepsis, you can read this article (link on website here). To summarize it, sepsis is a condition where people get very sick and overwhelmed with an infection. They also found out that among sick patients with sepsis, those with a fever had a better outcome than those without a fever.
In that study, the only people that have a worse outcome when suffering from pneumonia without a fever are those with a lower-than-normal temperature. It is the opposite of a fever and is called hypothermia. It happens in people with pneumonia who are very old, very weak, or very sick. These people not only don’t have enough energy to produce a fever, they also do not have enough energy to produce the minimum amount of heat needed to keep body temperature at normal.
If you have a family member who is elderly and frail, you can not rely on the presence or absence of a fever to decide if they have pneumonia. If he or she appears weaker, sicker, or more confused than usual, you need to call his or her doctor and seek medical attention right away.
Is pneumonia without a fever always dangerous?
No, absolutely not.
If you go back to the list of things that are needed to have a fever with pneumonia, the people with the worst outcome when suffering from pneumonia without a fever are the ones who are unable to have a fever due to problems in step 5 or step 6 of the sequence. These are those who cannot effectively reset the thermostat or those who can’t generate enough heat for a fever. You may have a mild viral pneumonia without a fever and you may not even know about it.
Among patients with mild, community-acquired bacterial pneumonia, a fever may or may not be present. Some of them have only had a cough, chest discomfort, and an increased heart rate. Others may only have weakness, dizziness, and a cough. When they only have mild symptoms, they can be treated with antibiotics at home regardless of whether they have pneumonia without a fever or with a fever.
Pneumonia is a disease that may only cause mild discomfort in some people, but can be a serious life-threatening illness in others. If you want to read about mild pneumonia and its treatment, you can read this other article.(missing link)
Here at PatientEducationMD, our goal is to explore different aspects of common but potentially serious medical issues, and pneumonia is one of the subjects we are exploring in great detail. If you would like to see a list of all of our articles on pneumonia, you can go to our “Diseases and Conditions” page and click on pneumonia.
References:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4944485/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5414343/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5197931/