Pope Francis said today that contraception could be justified in regions affected by the mosquito-born Zika virus.

Contraception could be "the lesser of two evils" in the context of the virus, which is spreading with alarming rapidity in Latin America, and probably causing some pregnant woman who are exposed to it to have babies born with a birth defect called microcephaly. The babies are born with, or grow up with, abnormally small heads and may have a range of developmental problems.

The Pontiff maintained that abortion is "an absolute evil" and should not be considered, even when the Zika virus is thought to have been contracted.

The Pope drew a comparison between this current crisis and the Humanae Vitae decree issued by Pope Paul VI, which enabled nuns to use contraception in Africa due to the risk of rape.

"Avoiding pregnancy is not an absolute evil," Francis said. "In certain cases, as in this one, such as the one I mentioned of Blessed Paul VI, it was clear.

"I would also ask doctors to do their utmost to find vacancies against these mosquitoes that carry this disease. This needs to be worked on."

The Pope spoke during an overnight flight on Wednesday en route back to Rome, following a six-day-long trip to Mexico.

His comments concerning contraception come in the context of the World Health Organisation advising that women in Zika-affected areas should avoid getting pregnant for the time being, whether through abortion or contraception. 

The traditional Catholic position on contraception is that using any artificial form is a sin.