In vector-borne disease, what does the Entomological Inoculation Rate (EIR) represent?

• A. The rate at which people are bitten by infectious mosquitoes.
• B. The total number of mosquitoes in a region.
• C. The average lifespan of mosquitoes.
• D. The percentage of mosquitoes carrying non-pathogenic microbes.

Answer: (A)

Entomological inoculation rate measures how often people are exposed to infectious mosquito bites. It combines two key pieces: how frequently people are bitten by mosquitoes (the human biting rate) and how many of those mosquitoes are carrying the pathogen (the infectious fraction among vectors). In malaria, for example, EIR is the product of the human biting rate and the sporozoite rate, giving infectious bites per person per day or per year. This directly reflects transmission pressure and is used to compare risk across locations or to assess the impact of control measures like bed nets or spraying. It’s not about the total number of mosquitoes, their lifespan, or mosquitoes carrying non-pathogenic microbes.