The Undying Lands have never heard of swine flu.  Well, not exactly...

VALINOR VIRUS

Location: Tol Eressëa
Fourth Age

Elrond left the hobbits’ sickroom and discovered Gandalf waiting in the corridor.

“How are they?” Gandalf asked anxiously. “I’ve never heard of anyone catching the Valinor Virus before.”

“Nor have I,” Elrond sighed. “From what I have been told, it usually passes harmlessly between the Eagles and the Mearas, with no transmission to Elves. Unfortunately, hobbits have no immunity, and they will be abed for several more days. Did you have to let them ride Shadowfax?”

“Are you blaming me for this?” Gandalf scowled.

“And you sent those Eagles to Mt. Doom!” Elrond realized. “Frodo must have been exposed twice! It took only the moist, tropical air here for the infection to bloom.”

“I’m a wizard, not a doctor,” Gandalf declared. “How could I know?”

“No matter,” Elrond said soothingly. “Bless Fëanor for inventing the fever-stick; I’m monitoring the hobbits’ temperatures as often as they’ll allow... which is not very often.” He frowned at the wizard. “You can take that fool mask off, you know. They are rather ineffective against this virus. Besides, you are one of the Istari!”

“So what?” Gandalf muttered darkly. “I've already died once, and don't plan to go through that a second time. I probably have no immunity either.”