Infectious Disease in Humans (chapter 11)

How Infectious Diseases spread

• Through droplets in the air

• By direct contact

• By contaminated food and water

Influenza

• Cause → Influenza is caused by influenza VIRUS

• How it is transmitted→ Influenza is transmitted through droplets in the air and when a person touches a object or surface contaminated with the virus and then touches his/her own eyes, mouth or nose.

• Signs and symptoms: Influenza produces signs and symptoms such as high fever,headache, stuffy nose, cough, sore throat and muscle aches.

Pneumococcal Disease

• Cause: Pneumococcal disease is caused by pneumococcal bacteria

• How it is transmitted: It is mainly transmitted though respiratory droplets

• Signs and symptoms: Fever, headaches vomiting, cough, chest pain and rapid breathing.

Vaccines

A vaccine contains an agent that resembles a pathogen and prevents infectious disease by stimulating white blood cells to quickly produce antibodies when pathogen invades.

How vaccines work

1. White blood cells binds to agent

2. White blood cell is simulated to divide

3. White blood cells produce antibodies.

4. Antibodies story the agent in vaccine.

5. Some of these white blood cells remain in the bloodstream. In future, if the live pathogens enter the bloodstream, the white blood cells will recognise them and quickly produce antibodies to destroy the pathogens before they can infect our cells.

How do antibodies work?

• Inhibits of bacterial cell wall→ when bacterial cell walls are weakened, water exerts the cell by osmosis. The cell expands, bursts and die

• Inhibit cell membrane function → by breaking bacterial cell me membrane. Without cell membrane, the bacterial cell is no longer protected from its environment as any substance can move into the bacterial cell

• Inhibits protein synthesis in ribosomes → antibiotics will bind to bacterial ribosomes, preventing the ribosomes from taking part in protein synthesis and inhibiting growth.

• Inhibits enzyme action in cytoplasm → bacteria require folic acid for growth. When the anntibiotics inhibit the enzymes needed for synthesis of folic acid. This will inhibit the growth of bacteria.

Why antibiotics can kill bacteria but not viruses

• Antibiotics act on bacterial cell wall. Viruses do not have cell wall

• They break up cell membrane. Viruses do not have cell membrane

• They actor on ribosomes, inhibiting protein synthesis and growth. Viruses do not have ribosomes and they do not grow.