Definition and Overview

The basic definition of an infection involves disease-causing agents invading the tissues of the body. These agents, which include prions, bacteria, parasitic organisms, viruses, and nematodes, typically multiply over a period of time, causing an immunological reaction in the host’s body. In humans, the body has its own immune system that automatically fights off the infection. However, in some cases when the infection is left unchecked and the patient’s immune system is unable to successfully fight the infection on its own, severe infection occurs.

Severe infection can manifest with symptoms that are easily observed, while some inapparent infections may have no visible symptoms yet still pose serious complications. There are also severe infections that are very contagious, infecting other individuals who come into contact with the patient. On the other hand, there are also severe infections that will not be passed on to other individuals and will instead affect a singular body.

Regardless of the source or contagiousness of an infection, it should be immediately treated as it could seriously damage or impair the functions of the patient’s organ systems. In some cases, severe infection can be fatal.

Cause of Condition

As mentioned, severe infections can be caused by a number of agents. These causative agents are often identified by the kind of signs and symptoms they produce. Here are some of the most common causative agents causing severe infection in humans:

  • Viruses and viroids - Viroids are independent particles of viruses, which can only replicate when they enter human cells. Research shows that viruses are closely associated with diseases from simple colds to devastating cancer. Typical virus infections in humans cause colds, cold sores, chickenpox, and influenza. More severe viruses can cause SARS, HIV, AIDS, Ebola, and bird flu. There are viruses that can cause chronic infections in patients, with the virus thriving inside the body and resisting the autoimmunological defenses. A patient can be affected by a severe viral infection when exposed to air or body fluids containing viroids, or when the viroids are introduced into the bloodstream through wounds or surgical procedures.

  • Pathogenic bacteria - These disease- and infection-causing microorganisms are closely linked to a wide variety of conditions, including tuberculosis, leprosy, diphtheria, syphilis, typhoid fever, and tetanus. These diseases are some of the most fatal bacterial infections, killing millions and millions of patients around the world.

  • Parasitic worms - These parasitic worms, including nematodes and helminths, typically infest the human digestive tract, but can live and thrive in different parts of the body and cause serious damage to tissues. Parasitic worms include roundworms, flukes, and tapeworms, and they usually come from contaminated water, contact with other individuals who have the parasites, contact with surfaces, locations, and objects where the microscopic eggs of the parasites were deposited, and food (usually meat and meat products, fruits, and vegetables).

  • Arthropods - Ticks, mosquitoes, fleas, and lice can carry bacteria and viruses that can cause a variety of infections in humans. The infections caused by arthropods are known as arboviral infections.

Even seemingly minor infections caused by these agents can have devastating effects on the patient’s body when left untreated. Severe infection can cause the shutting down of organ systems and, in some cases, death.

Key Symptoms

The symptoms vary from the agents that caused the infection. Some common signs and symptoms of severe infection that should raise alarm include the following:

  • Low body temperature
  • Fever, accompanied by shaking chills
  • Inflammation in certain body parts, which can be tender or even painful to the touch
  • Diarrhea
  • Decreased amount or need for urination
  • Rapid breathing
  • Nausea
  • Vomiting
  • Rapid pulse

Here are some common symptoms of the infection-causing agents described above:

  • Viral infections - Pain in the muscles and joints, headaches, loss of appetite, excessive sweating, clammy skin, cramps or pains in the abdomen (especially if the virus affects the gastrointestinal track), and weight loss

  • Bacterial infections - Frequent urination, blood in the urine (hematuria), symptoms similar to those of influenza, stiff neck, abscesses, lesions, rashes, general feeling of weakness, and irritability.

  • Worm infections - Enlarged liver and spleen, malabsorption of vitamins and nutrients in food, constipation or bowel obstruction, dehydration, cough, pain in the abdominal area, itchiness in the anus, anemia, neurological issues, irritability, and chest pains.

  • Arboviral infections - Severe forms of arboviral infection spread rather quickly and are characterized by symptoms like disorientation, high fever, convulsions, paralysis, and coma. Severe arboviral infections can lead to death.

One serious complication of severe infections is sepsis or blood infection. This is caused by an overwhelming immunological response to the infection affecting the body. Harmful biological chemicals are released by the immune system to the bloodstream, which can trigger widespread inflammation all over the body. This inflammation can then cause serious organ damage and blood clotting. The blood clots can deprive cells, tissues, and organs of much-needed oxygen and nutrients, leading to septic shock. A septic shock is potentially life-threatening as it drastically lowers the blood pressure, effectively shutting down the liver, kidneys, and lungs. Septic shock can lead to death.

Who to See and Types of Treatment Available

It is best to immediately consult with a doctor after observing the symptoms described above. In some forms of severe infection, strong antibiotics can be prescribed. These antibiotics will be taken orally or through intravenous drips for a specific period of time. In more serious cases, surgery can be performed.


  • Signore, EJNMMI Research: “About Inflammation and Infection.”
  • National Information Program on Antibiotics: “Bacterial vs. Viral Infections
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