The effects of experimentally induced respiratory virus infections on performance.

Studies of experimentally induced respiratory infections and illnesses showed that influenza impaired performance on a visual search task but had no effect on a simple motor task, whereas colds impaired the motor task but not the search task. The effect of influenza on the search task was observed in both volunteers with significant clinical symptoms and volunteers who were shown, by virological techniques, to be infected but who had no significant clinical illness. Performance was also impaired during the incubation period of this illness, which confirms that subclinical influenza virus infections can have behavioural effects. In contrast to influenza, the effects of colds were restricted to volunteers who had significant clinical symptoms, and the impairments in performance were observed only when the symptoms were apparent.