Question 1: Define measles and describe its main symptoms.

Answer: Measles is a highly contagious viral disease characterized by symptoms such as high fever, cough, runny nose, red eyes, and a distinctive rash.

Question 2: Explain how measles is transmitted from person to person.

Answer: Measles is transmitted through respiratory droplets when an infected person coughs or sneezes, and the virus can remain airborne for several hours.

Question 1: If a population of 10,000 people has a vaccination rate of 85%, how many people are unvaccinated? (Show your calculation.)

Answer: Unvaccinated = Total population - Vaccinated population = 10,000 - (0.85 × 10,000) = 10,000 - 8,500 = 1,500 people.

Question 2: A measles outbreak occurs in a community with 5,000 individuals, and 300 cases are reported. What is the attack rate expressed as a percentage? (Use the formula: Attack Rate = (Number of cases / Population) × 100)

Answer: Attack rate = (300 / 5000) × 100 = 0.06 × 100 = 6%

Question 1: Describe a simple experimental setup to test the effectiveness of a measles vaccine in a laboratory setting.

Answer: An experiment could involve two groups of cells or animals, one vaccinated and one unvaccinated, exposed to the measles virus. The effectiveness is determined by comparing infection rates in both groups, ensuring safety precautions are followed.

Question 2: Identify three variables that should be controlled in a vaccine efficacy experiment.

Answer: Variables include the age and health status of subjects, the dose of vaccine administered, and the environmental conditions during the experiment.

Question 1: In a community of 20,000 people, a vaccination campaign achieves 90% coverage. After several years, an outbreak reports 150 cases. Discuss how vaccination coverage affects the spread of measles.

Answer: Higher vaccination coverage reduces the number of susceptible individuals, thereby lowering the attack rate and preventing large outbreaks. Even with 90% coverage, some cases can occur, but the overall spread is limited compared to lower coverage scenarios.

Question 1: Describe the mechanism by which the measles virus causes symptoms in the human body. (6 marks)

Answer: The measles virus infects the respiratory tract and spreads through the bloodstream, triggering an immune response. The virus damages cells and tissues, leading to symptoms such as fever, cough, and rash. The immune response causes inflammation, which contributes to symptoms like high fever and rash. The virus’s replication in respiratory cells also facilitates transmission.

Question 1: Explain how the development of the MMR vaccine has changed the control of measles worldwide.

Answer: The MMR vaccine has significantly reduced measles cases and outbreaks globally by providing immunity to most of the population, leading to the eventual goal of eradication in many regions.