Environment: Infection and Response

Defining Disease

Diseases can be classified as either communicable (infectious) or non-communicable. Non-communicable diseases cannot be passed from one individual to another, while communicable diseases can be transmitted.
When a disease is caused by a pathogen such as a bacterium, virus, or fungus, it is referred to as an infectious disease.
Diseases may have social implications for families and communities, including the cost of medical treatment and time off work, or the possible need for ongoing care.

Pathogens and Disease

Pathogens are organisms that cause disease. These include specific types of bacteria, viruses, protists and fungi.
Each pathogen has a specific method of transmission, such as through air, direct contact, food, water or vectors like mosquitoes.
Many diseases have specific symptoms, which help in their identification. Malaria, for example, is caused by a type of protist and is characterised by fever, fatigue, vomiting, and headaches.
Antibiotics are drugs that can kill bacteria or inhibit their growth, but they are ineffective against viruses.

Vaccination

A vaccine provides active immunity to a disease by stimulating the production of antibodies without causing the disease itself.
The vaccine contains small amounts of dead or inactive forms of the pathogen, or toxins produced by the pathogen.
Herd immunity occurs when a large percentage of the population is vaccinated, making it difficult for a disease to spread within that population.

Body’s Defence Mechanisms

The immune system plays a crucial role in protecting the body from pathogens. It includes physical barriers like skin, chemical barriers like stomach acid, as well as cells and tissues involved in producing an immune response.
When pathogens breach the body’s initial defences, the immune system produces white blood cells that can ingest pathogens, produce antibodies, or produce antitoxins.
Antibodies attach to pathogens and either neutralise them, mark them for destruction by other white blood cells, or cause them to clump together.

Drug Development and Clinical Trials

Drugs must undergo rigorous testing before they can be used to treat diseases. This process involves several stages, including preclinical testing, where the drug is tested in the lab, and animal testing.
Clinical trials involve testing the drug in humans. Initial phases involve a small group to assess safety and establish a safe dosage. Further phases involve larger groups to assess efficacy and monitor side effects.

Remember to understand the main concepts, mechanisms, processes and key terms related to disease, pathogen, immunity and drug development to accurately grasp how organisms interact with their environment when it comes to infection and response.