Feeling feverish is never fun; and, when you have a fever, it’s likely that you want to find a way to make it disappear ASAP. According to Penn Medicine, the definition of a fever is a temporary rise in body temperature, typically in response to the body’s immune system fighting a foreign agent such as an invading microorganism. It’s normal for body temperature to change throughout the day due to digestion, exercise, climate, weather, hormones, and mere bodily functions that affect the body’s overall temperature. But when body temperature rises and remains higher than usual, a fever is often diagnosed, with the next step aimed at finding the root cause of the increase in body temperature. Figuring out the underlying cause of a fever is the first step in discerning how it needs to be treated so that you can get back to enjoying life fever free.
Both bacterial and viral infections are common reasons why a fever may spike, per WebMD. Microbes comprise bacteria and viruses, as well as millions of other microscopic organisms that live all around us, and even on or within us. When bacterial or viral microbes enter the body, the immune system can activate its protective forces that are meant to ward off the infectious organisms, thus resulting in a person experiencing a fever, among other symptoms such as fatigue, muscle aches, headache, and stomach upset. Here is what you should know about the symptoms and differences between bacteria-induced and virus induced fevers.
Bacterial and viral fevers differ in timing and duration
One way to make the distinction between a fever caused by bacteria and a fever caused by a virus is the length of time the fever persists. A fever from a virus tends to come on quickly and go away faster than a fever from a bacterial infection, according to Duke Health. Fevers with underlying viral causes can last up to two weeks but usually go away within 10 to 14 days at the latest. Some viruses, such as the flu virus, can be effectively treated with antiviral medication if identified within the first 48 hours of the onset of symptoms, thus shortening the duration of the fever even further.

Regardless of whether or not the medication is utilized at the onset of symptoms, a viral fever should typically begin to subside and symptoms generally improve within a few days. On the flip side, if a fever or other symptoms — such as nausea, vomiting, diarrhea, fatigue, or other indicators of illness — worsen as time passes, then the likelihood of an underlying cause from bacteria is increased.
Viruses like the common cold usually go away within a relatively short amount of time and don’t pose life-threatening harm (via WebMD). Sometimes, though, fevers caused by either bacteria or viruses can be accompanied by more severe symptoms that require urgent medical care or hospitalization, in which case a blood or urine sample may be taken or a culture test may be performed to determine whether viral or bacterial microbes are instigating fever. A tissue biopsy might also be needed.
Bacterial and viral fevers also differ in their symptoms
Fevers that worsen or linger longer than two weeks are likely to be caused by bacteria, especially if other symptoms of a bacterial infection are present. Cleveland Clinic advises that fever is the primary symptom of bacterial infections, but other frequent indicators include fatigue, chills, and headache. 

Identifying a fever caused by bacteria can be accomplished by paying attention to symptoms unique to specific types of bacterial infections and keeping track of new symptoms by taking notes to document the traits and length of each symptom. For example, a bacterial infection of the skin may cause a fever alongside a rash, redness, or blisters on the afflicted area of the skin. Other common bacterial infections are urinary tract infections (UTIs), which may have a fever accompanied by painful urination or odorous discharge from the urethra; pneumonia or pulmonary infections of the lungs, which often present with coughing, chest pain, or difficulty breathing in addition to fever; and gastrointestinal (GI) tract infections, which are associated with abdominal pain, stomach upset, vomiting, and diarrhea alongside symptomatic fever. 

When you’re feverish, documenting other symptoms can help determine if your fever is bacterial, especially if only one part of your body is affected. Since bacterial infections can spread through vectors such as insects like ticks and mosquitos, including recent outdoor activities in your documentation can help determine if your fever is due to a virus or bacteria.

Sharing notes with your doctor can be beneficial in obtaining a diagnosis and treatment plan. 
Read More: https://www.healthdigest.com/1167946/how-to-tell-if-your-fever-is-caused-by-a-bacteria-or-a-virus/