Infectious diseases

Infectious Diseases

Basics

  • Infectious diseases are caused by pathogenic microorganism such as bacteria, viruses, parasites or fungi.
  • These diseases can be spread from person to person, directly or indirectly.
  • Pathogens can also be transmitted through vectors such as mosquitoes.

Bacteria

  • Bacteria are single-celled microorganisms which can cause various diseases like tuberculosis, cholera, and pneumonia.
  • Bacteria can release toxins, which cause symptoms of the disease.
  • The body’s immune system usually responds to bacterial infection by producing white blood cells that destroy them.

Viruses

  • Viruses are smaller than bacteria and require a living host to replicate.
  • They introduce their genetic material into the cells and utilise the host’s cellular mechanisms to multiply.
  • Diseases caused by viruses include influenza, HIV/AIDS and COVID-19.
  • Viruses are usually fought off by the immune system but they can mutate to avoid detection.

Parasites

  • Parasites are organisms that live on or in a host organism and get their food at the expense of their host.
  • A few examples of parasitic diseases include malaria (caused by plasmodium parasite), leishmaniasis, and sleeping sickness.

Fungi

  • Some fungi are pathogenic and can cause diseases in humans like ringworm, and athlete’s foot.

Host Immune Response

  • The immune response is characterised by recognition of the infection, activation and response of immune cells like lymphocytes and macrophages.
  • The immune system produces antibodies in response to infection. These antibodies recognise and bind to the pathogens marking them for destruction.

Prevention & Treatment

  • Preventing infectious diseases include strategies like vaccination, good hygiene practices and use of antiviral or antibacterial drugs.
  • Vaccines stimulate the production of memory cells which recognize the pathogen if encountered again, making the immune response faster.

Epidemiology

  • Epidemiology is the study of determinants, occurrence, distribution and control of health and disease in a defined population.
  • This includes studying patterns of infectious diseases to implement control and prevention measures.
  • Important factors in disease spread include the population’s susceptibility, the proportion immunized, and rate of contact between susceptible and infected individuals.

Social & Economic Effects

  • The society and economy can be severely impacted by infectious diseases.
  • They can cause significant mortality, reduction in productivity due to illness, and high healthcare costs.
  • Pandemics, such as COVID-19, can have profound effects on global health and economics.