BRSV RNA detected in nasal swabs of cows that were naturally re-infected four years after a previous natural BRSV infection (n = 7, reinfection) and cows that were naturally infected for the first time (n = 5).

Samples were collected once and on the same day. All cows were housed in the same section of the loose range system. The unit TCID₅₀ equivalent (TCID₅₀ eq.) was used since the standard curve used in the assay was based on a BRSV-infected cell lysate with a known titre. Error bars represent standard deviation.

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