A single individual who "may have" been in the vicinity of Dallas Ebola victim Thomas Duncan was the reason Mexican officials turned away a Carnival cruise ship from docking in Cozumel. The ship is on its way back to the U.S.

A Carnival spokeswoman told the Washington Post the passenger was a health worker who may have been in contact with lab specimens from Duncan.

The Carnival Magic cruise ship was waiting off the coast of Mexico on Friday while waiting for word from the country's officials. After not hearing by noon, the ship turned around and headed to Galveston, Texas, its home, where it was due back by Sunday.

The health worker's identity has been undisclosed, but the cruise spokeswoman said she is in voluntary isolation despite not showing any signs of the virus.

"We greatly regret that this situation, which was completely beyond our control, precluded the ship from making its scheduled visit to Cozumel and the resulting disappointment it has caused our guests," Carnival said in a statement.

All passengers on the ship will be given a $200 credit and a 50 percent discount on a future cruise.

The worker has not showed any signs of the virus but had boarded the ship before U.S. health officials had declared an update to active monitoring of those who were in contact with Duncan in some way.

Health officials want the ship back in the U.S. as soon as possible, as a precaution, and are aware that the health worker was not in direct contact with Duncan. The State Department said that they are only concerned as a precaution because she may have been exposed to his specimens 19 days ago. A  doctor on board has confirmed she is in good health.

The news is one of the latest of concerns over the virus, which has killed more than 4,000 individuals mostly in West Africa, along with the U.S. and Spain.

Symptoms appear 21 days after the virus is contracted and is passed on through contact with bodily fluids such as sweat, blood, etc.

Other cases of travelers who have been in contact with Duncan have also been monitored, and some have showed signs of the virus.