Method for screening for an antiviral agent, by determining whether a potential agent interacts with a virus or cellular component which allows or prevents preferential translation of a virus RNA compared to a host RNA under virus infection conditions; and determining whether any interaction of the agent with the component reduces the level of translation of an RNA of the virus. The meter outputs a signal indicative of the turbidity of the fluid under test. The gear train includes a floating mechanism that permits the model locomotive drive wheels vertical freedom of movement, while still remaining mechanically linked to the gear train. The ground layer includes a ground pattern having at least one block on a surface of a substrate of the front end module.