These pigs had acquired lungworm infestations presumably containing masked influenza virus under natural conditions . 这些猪在自然条件下已受到含有隐蔽流感病毒的肺丝虫寄生。
2.
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“隐蔽病毒”的肺丝虫侵袭的猪，并不因肺丝虫的侵袭立即发生流感。
