Infection: Meaning, Types, Causes, Symptoms, and Treatment

Key Takeaway

• Microorganisms like viruses, bacteria, fungi, and parasites cause infections.
• Transmission of infections can happen by direct contact with an infected person, sharing an inanimate object with an infected person, exposure to pathogens in the environment, or ingesting contaminated substances.
• Infections generally cause symptoms like fatigue, fever, headaches, and muscle aches. However, in some cases, symptoms may be specific to the microorganism causing the infection. 
• Good hygiene is the key to preventing infections. Also, depending on the causative agent, doctors typically prescribe antibiotics, antifungals, antiparasitics, or antiviral medications to treat infections. 
• Inappropriate use of prescribed medications can lead to antimicrobial resistance (AMR), which is bad for humans because it causes microorganisms to develop resistance to medications originally designed to eliminate them. 

Microbes (microorganisms) like viruses, bacteria, fungi, and parasites are the primary cause of infections. Not all microbes in the body are harmful. Some of them are helpful for body functions like digestion. However, even the “good” bacteria can turn “bad” under certain conditions, leading to infections. 

There are different types of infections, according to the mode of transmission. Each infection type also has symptoms typically associated with it. This article delves deep into discussing infections, their types, how they spread, their symptoms, and if they can disrupt some natural body functions like menstruation and erections.

How infections spread

Infections usually occur when harmful microorganisms invade the body (the host) via the skin, mouth, eye, or genitals. These microorganisms come into contact with these routes by direct or indirect transmission.  

Direct transmission

Direct transmission of infection occurs when an infected person gets in close contact with an uninfected person. This close contact can be in the form of touching or skin contact, sexual intercourse, or kissing. 

Touching, especially handshaking, which is common, poses a risk of infection because the hands can come in contact with mucosal membranes like the eyes and exposed tissues via open wounds. Kissing and sexual intercourse can cause infections through fluid transfer. 

Fomite transmission

Fomite is a kind of transmission that involves the contamination of an inanimate object exposed to infectious agents that later come into contact with a susceptible person or animal. Some inanimate objects that can be exposed to pathogens include medical equipment, toothbrushes, clothing, or clippers. 

Aerosol or airborne transmission

When an infected person coughs or sneezes, they expose droplets of pathogens to the environment or body mucus membranes. Other people can inhale these droplets or touch the surfaces they have dropped on. 

Oral transmission

Oral transmission involves chewing or ingesting contaminated substances, including food, water, and inanimate objects. This kind of transmission is usually due to prior exposure of the ingested materials to waste materials and dirt that have already been exposed to harmful microorganisms. 

Types of infections

Different kinds of pathogens that vary in size, genetic makeup, function, shape, and how they affect the body cause infections. Four causative agents lead to the types of infections we have today: viral, bacterial, fungal, and parasitic.

1. Viral infection

Viruses that invade the body cells to replicate themselves cause viral infections. This process of virus invasion can damage, kill, or alter the infected cells in the body, and these changes manifest in the form of viral infection symptoms like sore throats, chills, and nasal congestion. 

In some cases, your immune system can fight off a virus to prevent it from replicating; thus, you show no symptoms of viral infection. However, sometimes, the infections may be more serious, causing severe symptoms or symptoms that last for longer periods of time.

Some types of viral infections include sexually transmitted infections (STIs), respiratory infections, neurological infections, congenital infections, viral hemorrhagic fevers, and digestive system infections. 

2. Bacterial infection

Single-celled organisms that can reproduce by themselves cause bacterial infections. Some bacteria are not harmful or do not cause illness, e.g., gut bacteria, which has several benefits in defense and regulation. Others are harmful.

Bacterial infections can cause food poisoning or gastroenteritis, ear, skin, and sinus infections, sexually transmitted infections (STIs), urinary tract infections (UTIs), and bacterial pneumonia.

3. Fungal infections

A fungal infection is also known as mycosis. It occurs when fungi invade the body such that the immune system cannot defeat them. Fungal infections usually develop on the skin or mucosal membranes (mouth, ears, nose, or genitals). Fungal infections typically cause skin changes in the area of the body affected, along with other symptoms.

4. Parasitic Infections

Parasites are micro or macro-organisms that need another organism (a host) for shelter and nutrients. Non-pathogenic parasites are parasites that can invade the human body without necessarily causing any harm, and they are usually found in the intestinal tract.  Pathogenic parasites will grow and reproduce inside the body, causing illness and parasitic infections. 

Three classes of organisms cause parasitic infections: helminths, protozoans, and ectoparasites. 

• Helminths, also known as worms, are multicellular organisms that can live inside and outside the body. Some examples of helminths include roundworms, flatworms, and tapeworms.
• Protozoa (pronounced proh-tuh-zoh-uh) are single-celled microorganisms that multiply inside the body and damage tissues. Plasmodium vivax, which causes malaria, is an example of a protozoa.
• Ectoparasites are organisms that live off your skin. They are not always disease carriers, but they are the direct cause of diseases because they infect the superficial layer of the skin and cause discomfort. Some examples of ectoparasites are fleas, ticks, and lice.  

Symptoms: What can an infection cause?

There are several infections with specific symptoms that will require your doctor’s diagnosis for identification. Some general symptoms of infections include:

• Headache
• Fever
• Fatigue
• Muscle ache
• Nausea
• Diarrhea

However, some symptoms can be specific to the type of infection present. Below are some additional symptoms associated with the different types of infections.

Symptoms of viral infections

Common symptoms of viral infections include:

• Warts 
• Blisters 
• Rashes
• Abdominal pain 
• Vomiting 
• Sore throat
• Cough
• Drowsiness
• High-fever

Symptoms of bacterial infections

Bacterial infections typically cause symptoms like:

• Redness
• Swollen or painful skin
• Shortness of breath
• Cough
• Chest pain
• Abdominal pain
• High-fever
• Confusion

Symptoms of fungal infections

Here are some common symptoms of fungal infections:

• Soreness and itching of the affected area
• White patches in the mouth or throat
• Pain while eating
• Discolored, thick, or cracked nails
• Cough
• Shortness of breath
• Painless lump under the skin

Symptoms of parasitic infection

Parasitic infections can cause symptoms like:

• Weight loss
• Increased appetite
• Chills
• Skin rash
• Severe headache or disorientation

How to prevent infections

Infections can affect anyone, causing mild or severe effects. However, people with certain health conditions, like heart disease and cancer, have a weakened immune system that makes them more susceptible to infections. Moreover, severe injuries expose body tissues and make people vulnerable to infections.

It is important for everyone to take the necessary preventive steps against infections to avoid severe effects or life-threatening complications. 

The best way to prevent infections is by practicing good hygiene. Here are some hygienic practices to prevent or minimize the risk of infections: 

• Wash your hands regularly after using the toilet, before and after eating, after coughing, sneezing, or blowing your nose, after playing with your pets, after getting soiled with dirt, and after visiting a sick person. 
• Cover your cough and sneeze with a tissue or disposable napkin. Don’t use your hands in the absence of these items; cough or sneeze into your elbow instead. 
• Wash any cuts you get, and visit your doctor for any severe injuries.
• Do not pick at healing wounds or squeeze pimples.
• Don’t share eating utensils like plates, spoons, and cups with others.
• Avoid contact with tissues, handkerchiefs, and other similar items used by others.
• Get vaccinated when necessary, and avoid taking shots in foreign places if you are a traveler.
• Use a latex or polyurethane condom during sexual intercourse with an untested partner, and speak to your sexual partner about regular testing for STDs, especially if you or they have sex with other people. 
• Properly wash fresh fruits and vegetables and thoroughly boil meat products. Cover exposed food until you are ready to consume it.

Treatment for infections

The appropriate treatment for an infection depends on the cause of the infection, which is why it is important to get a diagnosis from your doctor before seeking treatment. After a proper diagnosis, here are some treatment options your doctor may recommend:

•  Antibiotics: Antibiotics are medications used to treat bacterial infections.
• Antifungals: Your doctor may administer antifungals like fluconazole to treat common fungal infections.
• Antivirals: Antivirals are drugs used to rid the body of viral infection or, in some cases, ease the symptoms of infection. There are antivirals available for treating viral infections like human immunodeficiency syndrome (HIV), called antiretroviral therapy.
• Anti-parasitics: Antiparasitic drugs treat parasitic infections like those caused by worms and malaria.

Final thoughts: Antimicrobial resistance

Antimicrobials are medications (antibiotics, antivirals, antifungals, and anti-parasitics) that medical doctors prescribe to treat infectious diseases. The term antimicrobial resistance (AMR) is used to refer to when microorganisms develop mechanisms to combat the drugs assigned to kill them.  

Misuse of antimicrobials causes AMR and makes medications against infectious diseases ineffective. This can lead to a higher transmission rate and make infections increasingly difficult to get rid of.

AMR is an important reason not to self-diagnose or treat infections on your own but to always follow your physician's prescriptions. 

Anyone can develop infections, and there is no 100% strategy for preventing them. However, practicing good hygiene significantly reduces the risk of contracting infections.

If you suspect you have an infection, feel free to speak with a doctor so they can properly address your health concerns.