The woman started to show symptoms of the illness on Monday after arriving last week on the same flight as the first person in Lebanon to be infected with the coronavirus, the health ministry said in a statement.
Their plane had been carrying around 150 passengers and anybody who exhibited symptoms would be tested and quarantined, Health Minister Hamad Hassan has said. Others were instructed to remain isolated at home for 14 days.
Lebanon's government decided on Tuesday to restrict trips to countries with coronavirus outbreaks and halt all flights for pilgrims.
As the coronavirus spreads in the Middle East, several Arab countries have suspended certain flights and imposed shipping restrictions.
Iran reported 139 cases and 19 deaths on Wednesday, the most outside China, where the virus emerged in late 2019.The sudden rise in novel coronavirus cases in Italy, Iran and South Korea is "deeply concerning", but the virus can still be contained and does not amount to a pandemic, the World Health Organization (WHO) chief said on Wednesday.