Epidemiological studies of A-Hong Kong-68 virus infection in dogs.

Experimental inoculation of dogs with the A/Hong Kong/68 influenzavirus resulted in subclinical infection. The virus was readily passed to contacts in the same cage when the latter were exposed in the same inoculation room 24 hours after experimental infection. Removing the site of contact to a noncontaminated room or delaying contact until 48 hours after experimental inoculation greatly reduced the possibility of infection in contact animals. A survey of 271 canine serum samples obtained after a human epidemic from different geographical areas of the USA and the United Kingdom showed that 5.9% of the samples were positive; no positive reactions were found among 111 pre-epidemic samples. These studies demonstrated the laboratory and natural susceptibility of dogs to the Hong Kong variant and suggest the possible role of dogs in the epidemiology of human influenza.