Infectious Diseases

Infectious diseases are conditions caused by the presence and multiplication of pathogenic microorganisms in the patient’s—or host’s—tissues. Many are contagious, meaning they are transmitted directly from person to person, while others require a transmission vector to spread. Examples of infectious diseases include pneumonia and measles.

Depending on the causative pathogen, infectious diseases are classified as follows:

• Bacterial infection: Caused by bacteria—single-celled germs that reproduce quickly and may release toxins. Examples include strep throat, tuberculosis, and urinary tract infections.
• Viral infection: Caused by viruses—microscopic agents with a simple structure made of genetic material that infect cells and reproduce inside them. Examples include the common cold, AIDS, and COVID-19.
• Fungal infection: Resulting from contact with or inhalation of spores spread by fungi. Common examples include candidiasis and athlete’s foot.
• Parasitic infection: Caused by parasites such as protozoa or worms—microorganisms that live, feed, and reproduce within the host. Examples include malaria and dengue.
• Prion infection: Prions are not pathogens per se, but misfolded brain proteins that become abnormal, turning pathogenic and causing other proteins to misfold. They lead to extremely rare but fatal conditions such as bovine spongiform encephalopathy (commonly known as mad cow disease).

Additionally, based on the source of the pathogen, infectious diseases may be:

• Endogenous: The infectious agent is part of the normal microflora colonizing the host. A disturbance in the balance between host and agent can lead to infection, such as in candidiasis.
• Exogenous: The agent is introduced into the host from an external source, as in the case of the common cold.

Despite medical advances in managing them, infectious diseases remain a major public health concern due to their high morbidity, exacerbated by the emergence of new pathogens and the increasing resistance of microorganisms to antibiotics.

Symptoms

Symptoms of infectious diseases can vary widely depending on the cause, with each one presenting its own specific clinical manifestations. However, the most common general signs of infection include:

• Fever
• Fatigue, lack of energy, weakness
• Diarrhea
• Muscle aches
• Cough
• Rash
• Swelling
• Vision problems
• Respiratory issues

Causes

As previously explained, these conditions are caused by the spread of pathogens such as bacteria, viruses, fungi, or parasites. Contagious diseases can be transmitted through:

• Direct contact with infected people or animals, including transmission through the placenta or breast milk
• Indirect contact with contaminated surfaces
• Insect bites
• Consumption of contaminated food or water

Risk Factors

Anyone can contract an infectious disease, but the risk increases under the following conditions:

• Presence of immune system disorders
• Immunosuppressive treatments
• Prior invasive procedures, such as catheterizations, hemodialysis, or endoscopies
• Malnutrition
• Extreme ages (infancy or old age)
• Risky sexual practices
• Exposure to environments with potential transmission vectors, such as tropical insects or spoiled food and water
• Use of toxic substances or intravenous drug use
• Contact with infected people or animals

Complications

The prognosis of infections varies significantly—they can be very mild or severe enough to be fatal, as in cases of pneumonia, AIDS, or meningitis. Additionally, some infections are associated with an increased risk of developing certain types of cancer over time, such as HPV (Human Papillomavirus) or hepatitis B and C. Infectious diseases may also become dormant and reappear in the future.

Prevention

There are several ways to help prevent infectious diseases:

• Get vaccinated
• Wash hands frequently, especially before and after preparing or eating food and after using the bathroom
• Prepare food safely, maintaining hygiene and proper temperatures
• Practice safe sex by using condoms
• Avoid sharing personal items like toothbrushes, combs, straws, or cutlery
• Avoid contact with wild animals
• Do not consume food or water from unknown sources
• Travel responsibly, consulting a doctor about risks and necessary vaccines based on the destination

Which doctor treats infectious diseases?

Initially, symptoms are evaluated and treated by specialists in family medicine, internal medicine, or the check-up unit. If no clear diagnosis is made or the case is severe, the patient will be referred to the infectious diseases unit.