Which of the following statements is false?

• A. The very young and very old are at greater risk of many infectious diseases.
• B. A high dose of a pathogen is more likely to cause disease than a low dose.
• C. Herd immunity occurs when a population takes great care not to spread the disease (e.g. hand-washing, self-isolation etc.).
• D. A disease with a long incubation period might spread throughout a population before the population notices.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the concept of herd immunity. Herd immunity occurs when a significant portion of a population becomes immune to an infectious disease, either through vaccination or previous infections, thereby reducing the likelihood of disease spread to susceptible individuals.
2. Step 2: Recognize that herd immunity is not primarily achieved by behavioral measures such as hand-washing or self-isolation, although these actions help reduce transmission; instead, it depends on immunity levels within the population.
3. Step 3: Review the other statements: the very young and very old are indeed more vulnerable to infectious diseases due to weaker or less developed immune systems.
4. Step 4: Acknowledge that a higher dose of a pathogen generally increases the chance of infection because more organisms can overcome host defenses.
5. Step 5: Understand that diseases with long incubation periods can spread widely before symptoms appear, making early detection and control challenging.