Figure 4.

Replication and direct-contact transmission of H3N2 avian influenza viruses in guinea pigs. To test for virus replication, groups of two guinea pigs were inoculated with 10⁶ EID₅₀ of test virus in a 300-μl volume (150-μl per nostril). The animals were euthanized on Day 3 post-inoculation and their nasal washes and lung were collected for virus titration in eggs. The results are shown in panels a–e. To test for direct contact transmission, groups of three guinea pigs were inoculated intranasally with 10⁶ EID₅₀ of test virus, and 24 h later, three naïve guinea pigs were introduced into the same cage. Nasal washes were collected at the indicated times for detection of virus shedding, and seroconversion of the animals was confirmed by use of the hemagglutinin inhibition (HI) test. The virus shedding results are shown in panels f–j, and the HI antibody titres of the animals are shown in panels k–o. The horizontal dashed lines indicate the lower limit of detection. Each bar represents the virus titre or antibody titre from an individual animal.