What differentiates sporadic from epidemic disease?

• A. Transmission efficiency
• B. Host species
• C. Vaccine availability
• D. Geographic distribution

Answer: (A)

The key idea tested is how readily the infection spreads between people. Sporadic disease consists of isolated cases that occur irregularly with little to no secondary transmission. An epidemic arises when transmission is efficient enough to sustain a rapid, large rise in cases within a population, causing many secondary cases from each primary case. So, transmission efficiency is the defining difference: high efficiency enables the explosive spread characteristic of epidemics, while low efficiency leads to sporadic, scattered cases. Host species, vaccine availability, and geographic location can influence how outbreaks unfold, but they don’t determine the pattern as directly as how effectively the pathogen is transmitted.