Difference Between Flu and Sepsis

Influenza, commonly known as the flu, and sepsis are two distinct medical conditions that affect the human body in different ways. While the flu is a viral infection that primarily affects the respiratory system, sepsis is a life-threatening medical emergency that occurs when the body's response to an infection causes widespread inflammation throughout the body. In this essay, we will explore the differences between these two conditions, including their causes, symptoms, and treatments.

What is Flu?

The flu is also known as influenza and is an upper respiratory infection that is caused by a virus that can occur in different types. Type A and type B influenza viruses cause most illnesses. The flu does cause people to die each year due to complications. Recent mortality rates can be as high as 5% for the usual seasonal strains and types of flu, to as high as 60% for bird flu.

  • Flu Symptoms − Symptoms include a fever, chills, a cough, and often also pains and aches all over the body. Usually, there is also a headache, sore throat and weakness and sweating. Children may also experience vomiting and diarrhea along with the previous symptoms.

  • Diagnosis and causes for Flu − The flu is diagnosed with a physical exam, pulse oximetry, and chest X-rays. Molecular tests such as RT-PCR can definitively diagnose the strain of flu that is present. The flu is caused by a virus that is usually type A or typeB. T he exact type of flu virus changes each year.

  • Risk factors and complications − Certain people are at a higher risk of getting the flu. Usually, people older than 65, young children and people with weakened immune systems have a higher risk. However, this can vary with the strain of flu. Several complications can occur with the flu. Common complications include pneumonia, bronchitis, sinus infections, and ear infections. There is also a chance that the infection can cause heart and brain problems. Some of these complications such as pneumonia can lead to sepsis and possibly death.

  • Treatment for Flu − The best option is vaccination as this usually provides good protection from the flu. A vaccine can either prevent you from becoming ill or lessen the severity of the illness. There are antiviral drugs that can be given to reduce the severity of the illness. These work if given quickly. Vaccination is still the most recommended way to prevent the flu.

What is Sepsis?

Sepsis is the inflammatory response to some type of infection that is present in the body. In sepsis, chemicals are produced that can cause organ damage. Sepsis has quite a high risk of death with mortality varying from about 10% to as much as 40%.

  • Sepsis Symptoms − Sepsis includes symptoms such as a fever that is high and above 101oF. A person can also have chills because the temperature of the body can drop to lower than 96.8oF. There is also a fast respiratory rate and heart rate (more than 90 beats every minute).

  • Diagnosis and causes − Diagnosis is made by blood tests that indicate that there are a massive infection and inflammation throughout the body. Signs of infection include problems with the body’s electrolytes and the presence of substances in the blood that show kidney and liver problems and blood clotting problems. Sepsis is most often caused by severe infections in the abdomen including kidney problems. Blood infections and pneumonia can also lead to sepsis.

  • Risk factors and complications − Risk factors for sepsis include being elderly or very young, being very ill in the hospital and having a weakened immune system, also having a very bad injury such as a burn to the body. The presence of invasive medical devices such as indwelling catheters or breathing tubes also makes you susceptible to sepsis. Complications include reduced blood flow, clots, gangrene, and death.

  • Treatment for Sepsis − Sepsis is usually treated using powerful intravenous general antibiotics and sometimes medication to increase the blood pressure.

Differences: Flu and Sepsis

In this section, let us understand how Flu is different from Sepsis.

Causes: Flu and Sepsis

The flu is caused by the influenza virus, which can be spread through droplets when an infected person talks, coughs, or sneezes. The virus can also be transmitted by touching a surface contaminated with the virus and then touching one's mouth, nose, or eyes. Sepsis, on the other hand, is caused by the body's response to an infection. This response can be triggered by any type of infection, including bacterial, viral, or fungal.

Symptoms: Flu and Sepsis

The symptoms of the flu typically include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills, and fatigue. These symptoms can range from mild to severe and usually develop within one to four days after exposure to the virus. Most people recover from the flu within one to two weeks, but some people may develop complications such as pneumonia, which can be life-threatening.

Sepsis, on the other hand, is characterized by a combination of symptoms that can include fever or low body temperature, rapid heartbeat, rapid breathing, confusion, disorientation, dizziness, extreme fatigue, and decreased urine output. These symptoms can develop rapidly and worsen over time, and they may be accompanied by signs of organ dysfunction, such as low blood pressure, difficulty breathing, and abnormal liver function tests.

Treatment: Flu and Sepsis

The treatment for the flu typically involves getting plenty of rest, drinking fluids, and taking over-the-counter medications to relieve symptoms such as fever and cough. Antiviral medications may also be prescribed to people who are at high risk of developing complications from the flu, such as people with underlying medical conditions or people who are hospitalized with severe illness.

Sepsis, on the other hand, is a medical emergency that requires immediate treatment in a hospital setting. The first step in treating sepsis is to identify and treat the underlying infection that is causing the body's response. This may involve administering antibiotics or antifungal medications, draining abscesses, or performing other procedures to remove sources of infection from the body. In addition to treating the underlying infection, patients with sepsis may require supportive care, such as intravenous fluids, oxygen therapy, and medications to maintain blood pressure and organ function.

The following table highlights the major differences between Flu and Sepsis −





Flu is a viral infection that affects the respiratory tract.

Sepsis is a type of severe inflammatory response of the body to a massive infection.


Flu symptoms include a fever, chills, cough, sore throat, headache, aches and pains, and in children, vomiting, and diarrhea.

Sepsis symptoms include a high fever, chills, increased respiratory and heart rate, low blood pressure, nausea, confusion and reduced urination.


The flu is diagnosed by a physical exam, chest X-ray, pulse oximetry, and molecular tests.

Sepsis is diagnosed using blood tests that show signs showing infection such as abnormal results for the liver, kidney, and electrolytes.


The flu is caused by a virus that is usually of type A or type B.

Sepsis is caused by an injury or an infection that is very severe.

Risk factors

Risk factors for getting the flu include being over 65, being a young child, having a weakened immune system.

Risk factors for sepsis include having a severe illness and being sick in a hospital.


In conclusion, the flu and sepsis are two distinct medical conditions that affect the body in different ways. While the flu is a viral infection that primarily affects the respiratory system, sepsis is a life-threatening medical emergency that occurs when the body's response to an infection causes widespread inflammation throughout the body. Understanding the differences between these two conditions can help people recognize the signs and symptoms of each and seek appropriate medical care when needed.

Updated on: 12-May-2023


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