The 5 types of infections (causes and symptoms) - medical - 2023



Infectious diseases cause a major health problem around the world, despite the availability of effective vaccines and treatments. And as a button shows: COVID-19 has shown us that pandemics are not a thing of the past. However, there are many existing infections.

Without going any further, influenza and pneumonia are the eighth leading cause of death in countries like the United States and the situation worsens in countries with lower incomes, where respiratory tract infections, HIV and diarrhea are the three main causes of death. death. Infections are an especially important cause of illness among children, the elderly, and people with weakened immune systems.

This is where pathogenic microorganisms come into play, which have the ability to invade and multiply in the tissues of an organism to the point of making us sick. Each infection is different, and not all of them do not pose the same risk to people's health, but they can be classified according to the causative agent, which can diverge greatly from each other.

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What types of infections are there?

Pathogens belong to a wide variety of classes, but can be roughly divided into 5 groups: bacteria, viruses, fungi, parasites, and prions. Let's get to know each other a little better and see what the infections they cause are characterized by.

1. Bacterial infections

They are caused by bacteria, microscopic organisms made up of a single cell that lack a nucleus. Although there are many species that can cause disease in humans, less than 1% of existing bacteria are harmful.

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These unicellular organisms, although they are very simple, are self-sufficient, so they can perform all the functions necessary to survive by themselves. Sometimes, there are bacteria that have structures on their membranes that allow them to adhere and attach to the organs or tissues they infect, as well as extensions that allow them to move.

Bacteria that behave as pathogens can reach the human body in different ways (in the same way that harmless or beneficial do), either through contaminated water and food, through the air, through animals, Sexually or through direct contact with an infected person. In the same way, there are also bacteria that resist very well in the environment, so they can come into contact with us through objects.

Once inside the body, pathogenic bacteria can reproduce rapidly and cause diseaseIn addition, many of them release toxins that can damage tissues. Examples of bacterial infections are salmonellosis, bacterial gastroenteritis, gonorrhea, bacterial meningitis, cavities, botulism ...

The pathogenic bacterial species are so diverse and the diseases they can cause so many that it is very difficult to generalize when talking about the signs and symptoms. Many bacterial infections present with fever, if it is a gastrointestinal infection they usually cause diarrhea. They can also cause coughing, nasal congestion, throat irritation, and coughing.

Fortunately, bacterial infections can be treated with antibiotics. However, the misuse of these drugs is causing some bacteria to become resistant to the majority of existing antibiotics, something that especially worries the experts and that will bring us serious problems in the future.

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2. Viral infections

Viral infections are caused, worth the redundancy, by viruses, which is still debated whether they should be considered as living beings. Viruses are much smaller than bacteria and are so simple that they need to parasitize another cell in order to fulfill their replication functions. For this reason, viruses are called obligate parasites because if they do not infect other cells they cannot survive on their own.

There are millions of types of viruses, which have different forms since they affect different types of cells, so they can cause different diseases. For example, the virus that causes COVID-19 affects the lungs and respiratory system, while the polio virus affects the nervous system and mobility. Viruses that infect humans they usually have spherical shapesAlthough not all, and some may have a lipid envelope, such as the HIV virus and the flu virus, which helps to enter the host cell.

When a virus infects a cell, it multiplies and releases more viral agents to infect other cells and thus cause infections in the human body. Viruses can be transmitted through direct contact, through bodily fluids (blood, saliva, fluids) or secretions (urine, feces). People who touch infected objects or animals can also become infected.

For this reason, in the event of an epidemic, it is important to maintain good hygiene measures. However, not all viruses are equally infectious or use the same routes of transmission. For example, HIV is transmitted through sexual fluids but not through saliva. Therefore, it is vital to know well how each viral agent behaves in order to take the ideal precautions to protect ourselves against them.

Viruses are not treated with antibiotics Since these are not effective for these infectious agents, however, there are medications to treat some of your infections. They are called antivirals, which have the function of slowing down their development, although the immune system generally needs to neutralize and eliminate the infection.

In fact, some of the symptoms caused by viral infections, such as fever and tiredness, are sometimes the result of defense mechanisms activated by the immune system to fight the infection. Hence, vaccines are an excellent mechanism to prevent viral infections, since they involve training for the immune system so that it "learns" to identify and attack viruses more effectively.

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3. Fungal infections

Also called mycosisThese infections are caused by fungi, a very diverse group of organisms, since there are unicellular and multicellular fungi. Although these do not stand out for being pathogens, there are species capable of causing infections and causing diseases (which are unicellular forms).

They are distinguished from bacteria in that they have a cell wall similar to those of plants, but they do not photosynthesize, but are commensal and feed through the absorption of nutrients. They reproduce by budding and producing spores. They are usually experts in infecting superficial regions of our body, such as the skin or nails, although there are also species that colonize the genitalia or the digestive system.

When they manage to infect the human body, give rise to diseases that are not normally serious, but are very annoying and contagious. Human mycoses are usually classified according to the anatomical site in which they arise and according to epidemiology, endemic or opportunistic (vaginal candidiasis is an example). When they colonize internal organs such as the lungs, blood, or brain, they can cause potentially serious infections.

Yeast infections are treated with antifungals, which are usually quite effective. Even so, fungal infections are notorious for recurrence, which means that sometimes, even if the person is cured, the infection can reappear in a short period of time. Among fungal infections we find ringworm, dermatophytosis and athlete's foot.

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4. Parasitic infections

There are many species of human parasites that are capable of causing us infections since parasites are organisms that need to infect us to reproduce. A parasite is any organism that, to complete its life cycle, needs to infect another living being.

They are very varied forms of life since there are parasites of microscopic size to multicellular organisms such as worms or earthworms. On the one hand we find the protozoa, which are microscopic and unicellular and belong to the animal kingdom. They are usually transmitted through contaminated water or by the bite of a mosquito, as in the case of malaria. Protozoa are a major cause of illness and death in developing countries.

On the other hand there are helminths, which are more complex organisms and are also considered animals. People acquire these pathogens by accidentally ingesting their eggs, which are shed in the feces of infected people.

In countries where there are no adequate hygienic measures and no water sanitation, the spread of the eggs is very fast. However, there are effective treatments to cure helminthiasis. In countries with more resources, cases tend to be less frequent and tend to affect children, with ascariasis being the infection par excellence in daycare centers.

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5. Prion infections

Prions are infectious particles of a protein nature that have the ability to cause alterations in the body of animals. Surely it sounds more familiar to you if we talk about mad cow disease, as it is a disease caused by a prion. They are basically proteins with infective capacity.

Unlike the debate raised by viruses, prions are not considered living beings but they do have infective capacity, that is, they are capable of reaching a healthy person and causing a neurodegenerative disease. Humans can sometimes acquire these infective particles when they eat contaminated meat products.

These types of infections are very rare but extremely serious, as they are not curable and almost always fatal. In fact, Creutzfeldt-Jakob disease (better known as mad cow disease) is the only disease in the world with a 100% fatality rate. The prion causes a degenerative disease that begins to develop with personality changes, insomnia and progresses to memory loss and difficulty speaking, although it inevitably ends in death.

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