These pigs had acquired lungworm infestations presumably containing masked influenza virus under natural conditions.

这些然条件下已受到含有隐流感的肺丝虫寄生。

As a rule the swine infested with the lungworms carrying the "masked virus" did not develop swine influenza immediately upon infestation with the lungworm.

通常，受到携带了“隐”的肺丝虫侵袭的，并不因肺丝虫的侵袭立即发生流感。