The most common causes are viruses, bacteria, fungi and parasites. Infectious diseases usually spread from person to person, through contaminated food or water and through bug bites. Some infectious diseases are minor and some are very serious.
Treatment will depend on the cause of the infection. This article will focus on the most common and deadly types of infection: bacterial, viral, fungal, and prion.
The most deadly bacterial disease contracted by human beings is mycobacterium tuberculosis, the world's leading infectious disease with more than 1,700,000 deaths per year. As much as 13% of cases are resistant to most antibiotics, and about 6% are resistant or unresponsive to essentially all treatment.
Bacterial and viral infections can cause similar symptoms such as coughing and sneezing, fever, inflammation, vomiting, diarrhea, fatigue, and cramping -- all of which are ways the immune system tries to rid the body of infectious organisms.
Common sources of infection
Sources, e.g. airborne, blood borne, sexually transmitted, fecal, oral, environment, stagnant water, warm-water systems, animals.
1. Incubation. The incubation stage includes the time from exposure to an infectious agent until the onset of symptoms. Viral or bacterial particles replicate during the incubation stage.
For an infection to occur, germs must enter a susceptible person's body and invade tissues, multiply, and cause a reaction. Devices like IV catheters and surgical incisions can provide an entryway, whereas a healthy immune system helps fight infection.
Microorganisms capable of causing disease—pathogens—usually enter our bodies through the mouth, eyes, nose, or urogenital openings, or through wounds or bites that breach the skin barrier. Organisms can spread—or be transmitted—by several routes.
When germs get into a person's body, they can cause an infection. If you don't stop that infection, it can cause sepsis. Bacterial infections cause most cases of sepsis. Sepsis can also be a result of other infections, including viral infections, such as COVID-19 or influenza, or fungal infections.
Enterobacteriaceae, such as Klebsiella pneumoniae and Escherichia coli (E. coli) can cause serious infections of the urinary tract, bloodstream and wounds, and can also cause pneumonia. These infections are becoming difficult to treat because some bacteria have become resistant to all or most available antibiotics.
Viral gastroenteritis
This is an extremely contagious disease, caused by eating food or drinking water from contaminated utensils. Two of the common causes of viral gastroenteritis are rotavirus and norovirus. The symptoms can last anywhere between two and ten days or more.
Not washing your hands. Not scrubbing up after you use the bathroom or before you touch your nose and mouth can lead to repeat infections. That's especially true if you get colds or the flu often. It may seem like you're getting the same infection, but you might be getting infected with different viruses.
Tests that are frequently performed to help us with the diagnosis of a bacterial infection include a complete blood count and cultures of fluid that we are concerned about. This may include a blood culture, urine culture, or spinal culture (which requires a spinal tap).
As discussed, if your symptoms are caused by a virus (like a cold or flu virus), you won't need antibiotics. But if you have a sore throat due to bacteria — for instance, strep throat or bacterial tonsillitis — you will need antibiotics.
A bacteria culture is a test to confirm whether you have a bacterial infection. The test can also identify what type of bacteria caused the infection, which helps guide treatment decisions. For a bacteria culture test, a healthcare provider takes a sample of blood, stool, urine, skin, mucus or spinal fluid.