Understanding Infections, Immunity and Disease Prevention

Pathogens and Disease

Pathogens are microorganisms that can cause disease in plants and animals. The main types of pathogens include:

• Bacteria: Single-celled prokaryotes that can cause diseases like tuberculosis and food poisoning.
• Viruses: Non-living particles that hijack host cells to replicate, causing diseases like influenza and COVID-19.
• Fungi: Multicellular eukaryotes that can cause athlete's foot and ringworm.
• Protists: Single-celled eukaryotes like the malarial parasite Plasmodium.

Pathogens can be transmitted through various routes, including direct contact, body fluids, air, water, and vectors like mosquitoes.

Body Defences and Immunity

The body has several lines of defence against pathogens:

• Physical barriers like skin and mucous membranes prevent entry.
• Phagocytes like white blood cells engulf and destroy pathogens.
• Antibodies produced by plasma cells bind to and neutralise pathogens.
• Memory cells allow a rapid immune response upon re-exposure.

Vaccination and Treatment

Vaccines contain weakened or inactive pathogens that stimulate an immune response without causing illness. This prepares the body to fight future infections.

Antibiotics and antivirals help treat bacterial and viral infections, respectively. However, antibiotic resistance is a growing concern due to the misuse of antibiotics.

Plant Diseases

Plants also face threats from pathogens like fungi and bacteria, which can severely impact crop yields. Measures like crop rotation, pesticides, and breeding resistant varieties help combat plant diseases.