What to know about infections

common cold infection

An infection develops when a microbe penetrates a person’s body and causes damage.

The microbe takes advantage of the person’s body in order to survive, reproduce, and colonize. Pathogens are small infectious organisms that are contagious and have the ability to grow rapidly. Pathogens include, for example, the following:

  • fungi
  • viruses
  • bacteria

They have the ability to spread in a variety of ways, including the following:

  • the transfer of bodily fluids
  • skin contact
  • touching an object that a person carrying the pathogen has also touched
  • inhaling airborne particles or droplets
  • contact with feces
  • ingesting contaminated food or water

In this post, we will discuss the numerous types of infections, how to limit the risk of infection, and the symptoms that they produce.


common cold infection
The common cold is a viral infection of the respiratory tract.

The pathogen responsible for an infection and the consequences of an infection on the human body are determined by the pathogen’s characteristics.

The immune system is a very efficient barrier against infectious agents, protecting the body from infection. Pathogens, on the other hand, can occasionally outstrip the immune system’s ability to defend itself against them. An infection has progressed to the point where it is potentially hazardous.

Some pathogens have no impact at all on the host. While others create poisons or inflammatory molecules, these substances cause the body to respond negatively. Consequently, some infections are minor and scarcely detectable, while others are serious and life threatening in their severity. Some pathogens are resistant to treatment, whereas others are not.

Infections can spread in a number of different ways.

Pathogens are classified into four categories: bacteria, viruses, fungi, and parasites. There are various differences between them, including:

  • what effect they have on the body
  • shape
  • function
  • size
  • genetic content

Viruses, for example, are far smaller than bacteria. They infiltrate and take over cells of a host, whereas bacteria may thrive without the presence of a host.

The treatment for the infection will be determined by the source of the illness. This article will cover the most frequent and dangerous kinds of infection, including bacterial, viral, fungal, and prion infections.

Bacterial infections

Bacteria are single-celled microorganisms, also known as prokaryotes, that live in the environment.

There are at least 1 nonillion bacteria on the planet, according to experts’ estimations. A nonillion is a 1 followed by 30 zeros. Bacteria make up a large portion of the Earth’s biomass.

Bacteria may be classified into three types:

  • Spherical: These are known as cocci.
  • Rod-shaped: These have the name bacilli.
  • Spiral: Coiled bacteria are known as spirilla. If the coil of a spirillum is particularly tight, scientists call it a spirochete.

It is possible for bacteria to survive in practically any sort of environment, ranging from severe heat to extreme cold, and some strains have even been shown to thrive in radioactive waste.

There are billions of bacterium strains, but only a handful of them are known to cause illness in humans. Some of them are able to survive inside the human body, such as in the stomach or airways, without causing any harm to the individual.

In certain cases, “good” bacteria can fight off “bad” bacteria and keep them from causing illness. Some bacterial illnesses, on the other hand, can be deadly.

These are some examples:

The following are some instances of bacterial infections:

Antibiotics can be prescribed by a doctor to treat bacterial illnesses. Some strains, on the other hand, develop resistance and are able to withstand the treatment.

Viral infections

Viral infections arise as a result of being infected with a virus. Although it is possible that millions of distinct viruses exist, researchers have only found around 5,000 different varieties thus far. Viruses carry a little bit of genetic information, and they are protected by a coat of protein and lipid (fat) molecules that coats their surface.

Viruses infiltrate a host and attach themselves to the cells of the host. When they enter the cell, they release the genetic material that they carried with them. The presence of this substance causes the cell to reproduce the virus, which results in the virus multiplying. When a cell dies, it releases new viruses into the environment, which then infect new cells.

Not all viruses, on the other hand, are capable of destroying their host cell. Some of these alter the cell’s function, while others do not. Some viruses, such as the human papillomavirus (HPV) and the Epstein-Barr virus (EBV), have the potential to cause cancer by causing cells to reproduce in an uncontrolled manner.

It is also possible for a virus to target certain age groups, such as newborns or early children.

Viruses can be latent for a period of time before reactivating and reproducing. The individual who has been infected with the virus may appear to be completely healed, but they may become ill again if the virus reactivates.

Viral infections include the following:

  • the common cold, which is caused mostly by viruses such as rhinoviruses, coronaviruses, and adenoviruses
  • encephalitis and meningitis, resulting from enteroviruses and the herpes simplex virus (HSV), as well as West Nile Virus
  • warts and skin infections, for which HPV and HSV are responsible
  • gastroenteritis, which norovirus causes
  • COVID-19, a respiratory disease that develops after a novel coronavirus infection that is currently causing a global pandemic

Other viral conditions include:

  • Zika virus
  • HIV
  • hepatitis C
  • polio
  • influenza (flu), including H1N1 swine flu
  • Dengue fever
  • Ebola
  • Middle East respiratory syndrome (MERS-CoV)

Antiviral drugs can be used to alleviate the symptoms of some viruses while the sickness is still active and healing. They have the ability to either inhibit the virus from multiplying or enhance the immune system of the host, allowing it to better combat the infection’s effects.

When it comes to viruses, antibiotics are ineffective. These medications will not prevent the virus from spreading, and their usage raises the likelihood of antibiotic resistance.

The majority of treatment focuses on alleviating symptoms while the immune system fights the infection on its own, without the intervention of drugs.

Fungal infections

When it comes to fungi, they are often multicellular parasites that degrade and consume organic materials through the use of enzymes. Some varieties, such as yeasts, are, on the other hand, single celled.

Fungi usually always proliferate by spreading single celled spores, which are spores with one cell. It is common for mushrooms to have long and cylindrical structures with several tiny filaments branching off from the main body.

There are about 5.1 million different species of fungus.

Several fungal infections begin in the surface layers of the skin, and some of these infections spread to the deeper layers of the skin. The inhalation of yeast or mold spores can occasionally result in fungal illnesses such as pneumonia, or more widespread infections throughout the body, according to the CDC. Systemic infections are another term for this type of illness.

The body normally has a population of beneficial bacteria that contribute to the preservation of the delicate balance of microorganisms. Intestines, mouth, vagina, and other regions of the body are lined with these cells.

A fungal infection is more likely to occur in those who are at risk for the following factors.

  • use antibiotics for a long time
  • have a weakened immune system, due, for example, to living with HIV or diabetes or receiving chemotherapy treatment
  • have undergone a transplant, as they take medications to prevent their body from rejecting the new organ

Examples of fungal infections are:

  • valley fever, or coccidioidomycosis
  • histoplasmosis
  • candidiasis
  • athlete’s foot
  • ringworm
  • some eye infections

A rash may indicate a fungal infection of the skin.

Prion disease

A prion is a protein that does not contain any genetic information and is generally considered to be harmless. Prions are not considered to be living microorganisms by scientists. Prions can, however, fold into an aberrant form and become a rogue agent, infecting the host and causing the illness.

Pranins have the potential to alter the structure of the brain as well as other components of the nervous system. They do not reproduce or feed on the host’s resources. Rather, they cause aberrant activity in the cells and proteins of the body as a result of their presence.

All of these disorders are caused by prions and are now lethal. Prions cause degenerative brain diseases that are all uncommon but advance swiftly and are currently fatal. They include bovine spongiform encephalopathy (BSE), sometimes known as mad cow disease, and Creutzfeldt-Jakob disease, which is a kind of neurodegenerative illness (CJD).

Researchers have also discovered a relationship between prion infection and some occurrences of Alzheimer’s disease.

Other infections

Even though the sorts of infection that we have discussed above are the most common, there are other types of infection that can have an impact on the body, as well.

A protozoan infection can be caused by a single celled organism that has a nucleus. Protozoa frequently exhibit characteristics that are comparable to those of animals, such as motility, and they have the ability to exist outside of the human body.

The most prevalent way in which they spread to other individuals is by excrement. Infection with a protozoan, such as amebic dysentery, is one example.

If a helminth is fully matured, it is likely to be visible to the naked eye because of its size and multicellular nature. Flatworms and roundworms are two types of parasites that fall within this category. These are also capable of causing infection.

Finally, ectoparasites, which include mites, ticks, lice, and fleas, can transmit illness to humans and animals by clinging to or burrowing into their hosts’ skin. Ectoparasites can also include blood-sucking arthropods, such as mosquitoes, which spread sickness by ingesting human blood and transmitting it to other people.


Whichever sort of organism makes its way into the body is the root cause of an infection. Viruses, for example, can create a viral infection if they infect a certain host.

The immune system’s attempt to rid the body of the invading organism causes the symptoms of an infection to manifest themselves, such as swelling and a runny nose.

When white blood cells rush to the site of an injury in order to resist invading microorganisms, for example, a wound might become infected and fill with pus.


It is dependent on the organism that is causing the illness, as well as the place where it is occurring, on the symptoms of an infection.

Cells in the genitals or upper respiratory tract are targeted by viruses, which is why they are called “target cells.” The nervous system is targeted by viruses such as the rabies virus. Some viruses attack skin cells, resulting in the formation of warts.

Many others target a broader spectrum of cells, resulting in a variety of symptoms. Runny nose, muscular pains, and an unsettled stomach are all common symptoms of the flu virus.

A person suffering from a bacterial infection will frequently have symptoms such as redness, heat, swelling, fever, and discomfort at the location of the infection, as well as enlarged lymph nodes.

A rash on the skin may be indicative of a fungal infection of the skin. Viruses and bacteria, on the other hand, can cause skin problems and rashes as well.

The quick development of brain damage, memory loss, and cognitive impairments that are characteristic of prion illnesses are among the most common symptoms. They can also cause the formation of plaque in the brain, which can result in the organ’s decomposition and eventual death.


There is no one strategy that can be used to prevent all types of infectious illnesses. People should, on the other hand, take the following precautions to limit the danger of transmission:

  • Hands should be washed often, particularly before and after preparing meals and after using the restroom.
  • While cooking a meal, keep all surfaces clean and avoid storing perishable food at room temperature for an extended period of time.
  • Take any necessary vaccines and be sure to keep them up to date on them.
  • Only take antibiotics if you have a prescription, and make sure to finish the entire course of treatment, even if your symptoms heal sooner than expected.
  • Especially important is to disinfect places that may contain large concentrations of germs, such as the kitchen and bathroom.
  • Prevent the spread of sexually transmitted infections (STIs) by having frequent STI tests performed, wearing condoms, or by refraining from sexual activity entirely.
  • Personal things such as toothbrushes, combs, razor blades, drinking glasses, and culinary utensils should not be shared with others.
  • Follow your doctor’s recommendations when traveling or working while suffering from an infectious ailment, as doing so might result in the spread of the sickness to others.

A healthy lifestyle that includes regular physical activity and a nutritionally balanced diet can assist to maintain the immune system robust and prepare the body to defend itself against many sorts of illness.


  • https://www.cdc.gov/parasites/about.html
  • https://medlineplus.gov/bacterialinfections.html
  • https://www.medicalnewstoday.com/articles/196271
  • https://bsapubs.onlinelibrary.wiley.com/doi/full/10.3732/ajb.1000298
  • https://nihrecord.nih.gov/2019/03/08/alzheimers-disease-prion-diseases-share-similarities
  • https://www.ncbi.nlm.nih.gov/pubmed/15190676
  • https://www.cdc.gov/fungal/index.html
  • https://microbiologysociety.org/why-microbiology-matters/what-is-microbiology/fungi.html
  • https://eol.org/docs/discover/viruses
  • http://www.woundcarecenters.org/article/wound-types/infected-wounds
  • http://kidshealth.org/en/parents/infections/
  • https://www.cdc.gov/nchs/fastats/infectious-disease.htm
  • https://www.pugetsound.edu/student-life/counseling-health-and-wellness/health-topics/preventing-the-spread-of-infec/
  • https://wwwnc.cdc.gov/travel/page/before-travel
  • https://www.cdc.gov/fungal/diseases/index.html
  • https://www.cancer.org/cancer/cancer-causes/infectious-agents/infections-that-can-lead-to-cancer/viruses.html
  • http://kidshealth.org/en/kids/germs.html