THE 10 MOST COMMON MICROBIAL DISEASES - MEDICINE - 2025

The microbial diseases are diseases caused by microorganisms in various ways that affect humans and animals. These tiny microorganisms are commonly called microbes or germs, and this group includes bacteria, fungi, viruses, protists, and others.

The diseases produced by these microbes are known as infectious diseases and are mainly fought with the use of antibiotics or antivirals. The famous French scientist Louis Pasteur was the one who discovered the microbial theory of disease in the mid-19th century.

Today it is accepted that microorganisms are the cause of most of man's diseases, but at the time that Pasteur raised this theory, it was still believed that diseases were produced by fetid emanations from water or soil, or by an increase or decrease in body fluids (bile, phlegm and blood).

About half of the diseases known today are of microbial origin. The forms of contagion are very varied, but the most common are acquired by ingesting contaminated food or water or by direct transmission from a sick person to a healthy person.

Most common microbial diseases

The influenza virus is very common today. This virus attaches itself to the membrane of a human cell, enters and binds to the cell, releasing fragments of RNA (ribonucleic acid); These fragments carry the genetic information copied with the virus, spreading rapidly and infecting new cells.

There is a vaccine to fight the flu or, in any case, to alleviate symptoms in case of infection. The flu virus is constantly mutating, so the vaccine formula must also be changed frequently.

The symptoms are not serious but they are bothersome: mucus, cough, general malaise and, sometimes, fever.

2- diarrhea

It is transmitted by the E. Coli bacteria, through the ingestion of poorly washed food.

E. Coli lives in the intestines of cattle and is eliminated through their feces, so that food of plant origin (in direct contact with the ground) can be easily contaminated and that is why it is essential to disinfect them very well before to consume them.

It is an inflammation of the conjunctiva of the eyes caused by the adenovirus Haemophilus influenzae and many other pathogens, whether bacterial or viral.

It is quite common in people who use contact lenses, due to poor cleaning and disinfection of them. Other microbial diseases of the eye are: keratitis, herpetic keratitis or trachoma.

4- Meningitis

Pneumococcal Meningitis is a devastating infectious disease that affects the nervous system. It can be life threatening and progresses rapidly, especially in young children and the elderly.

It is caused by pneumococcus, a bacterium that also causes pneumonia and is found asleep in about 70% of people. It is usually very resistant to antibiotics, although there is a vaccine that has proven to be quite effective.

Other microbial diseases that affect the nervous system are: encephalitis, rabies, poliomyelitis and tetanus.

There are many types of herpes that are microbial infections that affect the skin; herpes simplex is the most common (HSV-1, skin and HSV-2, genital).

Research shows that about 90% of Americans are infected.

Most of the cases are subclinical (not reported or treated) and the remaining 10% is the one with visible and annoying symptoms such as sores or short-lived lip vesicles that are often mistaken for canker sores.

It is transmitted by contact with saliva and by sexual contact, in the case of herpes HSV-2. The danger of this disease is that, if it is not treated promptly, it can lodge in the brain and cause severe and even fatal herpetic encephalitis.

6- Tuberculosis

It is caused by a bacterium called Koch's bacillus in honor of its discoverer. Its contagion can occur through direct contact with already infected animals (dogs, cats, birds, pigs, cows) or from man to man via the lung when breathing near an infected person who coughs, sneezes or simply contaminates the surrounding atmosphere.

To a lesser extent, it can be transmitted by ingestion of contaminated food. Most of those infected with tuberculosis do not have symptoms, but if they do, the most obvious is a strong cough (sometimes with the presence of blood), fever, night sweats and weight loss due to lack of appetite.

Treatment applies only to symptomatic patients and is usually long and with a potent combination of several antibiotics.

Also called Salmonella from the name of the microorganism that produces it. It is acquired by ingestion of contaminated food and produces acute febrile gastroenteritis, which includes severe abdominal pain, diarrhea, moderate fever, and chills.

Eventually headaches and vomiting also appear. It can be serious in children and the elderly, mainly due to the risk of rapid dehydration and can become fatal if the microorganism passes from the intestine into the bloodstream. It can be avoided by washing and cooking food thoroughly before eating it.

8- AIDS

It is the virus of the 20th century. HIV or Acquired Immunodeficiency Virus is a retrovirus with a long incubation period that affects blood cells and the nervous system, in addition to suppressing the immune system.

This virus is transmitted through the bloodstream, so a person can only become infected by direct contact through the blood.

Saliva or semen are not vehicles of transmission per se, but there is a high risk of these fluids passing into the bloodstream through tiny ulcerations on the skin or mucous membranes.

Thanks to the intense scientific research of the last 30 years, although it has not been possible to find a cure for this disease, it has been possible to obtain powerful drugs to keep it at bay and lower its incidence of mortality, which was very high in the last quarter of the last century.

There are several types of this disease (A, B, C, D and E), but the common denominator of all is that it affects the liver and that they are highly contagious. The most common symptoms are jaundice (the skin turns yellow), tiredness and general malaise.

It requires preventive isolation and a lot of rest. Acute hepatitis A and E are not treated clinically because in most cases they heal spontaneously.

Hepatitis B is transmitted by direct contact with blood (transfusions or shared syringes), by sexual contact, or from mother to child during pregnancy or delivery. 90% of hepatitis B are curable, in part because there is a very effective vaccine.

10- Chickenpox

It is an eruptive disease caused by the Varicella Zoster virus, which mainly affects children under 15 years of age. It is highly contagious by skin contact, so the patient must be isolated immediately.

It can include headaches and fever, but the most common symptom is pustules all over the body that are often very itchy. In adults, pregnant women, or people with a weakened immune system, the disease can have more serious consequences.

There is an effective vaccine to ease symptoms. It is a disease that does not recur in the same person.

References

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2. Ma. Del Rosario Pascual Anderson (2005). Foodborne diseases: their prevention. Díaz de Santos editions.
3. Tuberculosis Disease (TB): Symptoms and Risk Factors. Centers for Disease Control and Prevention. Recovered from cdc.gov.
4. Diseases: microbial theory, infectious agents, modes of transmission. Recovered from apuntes.com.
5. Hepatitis. University of Navarra Clinic. Recovered from cun.es.
6. Chickenpox. Recovered from medlineplus.gov.
7. Omar Niño (2011). Microbiology. Recovered from omarleo168-microbiologia.blogspot.com.ar.
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9. Microbial theory of disease, Miasmatic theory of disease and Theory of the four humors. Recovered from es.wikipedia.org.