Which factor contributes to the high contagiousness of FMD in terms of inoculum?

Which factor contributes to the high contagiousness of FMD in terms of inoculum?

• A. It requires only about 10 virions to infect
• B. It requires thousands of virions
• C. It requires a specific host receptor
• D. It requires a vaccinated animal to spread

Answer: (A)

The key idea is that infectious dose drives how easily a virus spreads. Foot-and-mouth disease virus can establish infection in a susceptible animal with an extremely small number of virions, around ten. That means even tiny exposures from saliva, aerosols, or contaminated surfaces can start infection, allowing rapid transmission within a herd. The virus is also shed abundantly by infected animals and remains relatively stable in the environment, which further amplifies spread after that tiny initial dose. So, the best answer reflects how a very low inoculum can spark infection, explaining the high contagiousness.

The key idea is that infectious dose drives how easily a virus spreads. Foot-and-mouth disease virus can establish infection in a susceptible animal with an extremely small number of virions, around ten. That means even tiny exposures from saliva, aerosols, or contaminated surfaces can start infection, allowing rapid transmission within a herd. The virus is also shed abundantly by infected animals and remains relatively stable in the environment, which further amplifies spread after that tiny initial dose. So, the best answer reflects how a very low inoculum can spark infection, explaining the high contagiousness.