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Summary
Twelve New Zealand isolates of avian Infectious Bronchitis virus were typed by the serum-neutralization test. Both the constant serum decreasing virus and the constant virus decreasing serum methods were used. Cross-protection tests in specific-pathogen-free chickens were also carried out.
Four groups of viruses, designated serotypes A, B, C and D were distinguished by both methods. Immunization with B, C and D gave some protection to challenge with type A.