Scientists have not yet concluded whether a newly discovered virus is airborne, or if it can only be transmitted through infected blood. If it does prove to be airborne, they fear that hundreds of people may have already been infected. Since it is almost impossible to detect in its early stages, it is possible the virus may spread rapidly. Therefore, if it is an airborne virus, it will be almost impossible _________.


Which of the following statements best completes the paragraph above?

to tell how many people have been exposed to the virus
to stop its spread
to find a cure
to detect
to employ research experts