Infection of monocytes with Udorn was not dependent on the presence of lymphocytes, as monocytes isolated using CD14+ immunomagnetic selection incubated with Udorn (MOI = 2) showed a similar HA expression at 8 h p.i. to gated monocytes in MNC samples (48.7±5.5 (n = 3) and 47.1±6.5 (n = 9), respectively; data not shown). Here, CD14 is linked to infection.