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.