Most common cause of pink eye can remain latent in host Macrophage.

http://en.wikipedia.org/wiki/Macrophage

Adenovirus (most common cause of pink eye) can remain latent in host macrophage, with continued viral shedding 6–18 months after initial infection.
Brucella spp. can remain latent in macrophage via inhibition of phagosome–lysosome fusion; causes brucellosis (undulant fever).