The 2nd US patient is a health worker from Saudi Arabia, which saw 18 new cases.
Also, the Saudi agriculture ministry for the first time offered MERS-CoV camel precautions.
Most of the new cases occurred among young adults in Jeddah and Riyadh, half of them asymptomatic.
Lebanon confirms its first case, while Saudi Arabia reports 14 more, with 5 deaths.
A hospital official said the first US MERS patient had some non-respiratory symptoms before he left Saudi Arabia.
As Saudi Arabia reports 28 new MERS cases, experts point up infection control issues in hospitals.
Camel populations in Kenya have had antibodies to the Middle East respiratory syndrome coronavirus (MERS-CoV) as far back as 1992, according to an international research team that tested stored samples, according to a study yesterday in Emerging Infectious Diseases.
Cases continue in Middle East hot spots as first US case-patient recovers.
The first US MERS patients is a US citizen in his 60s who lives and works in Saudi Arabia.
Saudi Arabia reported 36 cases over the past 3 days, pushing its total well over 400.
