Can the ingestion of a single virus particle cause infection in humans?

The ingestion of a single virus particle can indeed cause infection in humans, making this statement true. Certain viruses have a low infectious dose, meaning they can initiate an infection with just a small number of particles. For instance, norovirus and some strains of enteric viruses are known to be highly infectious, with reports indicating that doses as low as a single viral particle can lead to illness.

This phenomenon occurs due to the ability of viruses to replicate within the host after entry, thereby creating an exponential increase in viral particles once inside. The likelihood of a single viral particle causing infection can vary based on several factors including the specific virus in question, the host's immune response, and the context of exposure (such as the route of ingestion and the host's overall health). However, the general principle highlights that even a single virus particle has the potential to result in an infection under the right conditions.