90-Second Read: American cruise passenger tests positive for Hantavirus. Live updates

At least 18 people are currently under observation at two of the nation's top medical centers after being potentially exposed to Hantavirus aboard the MV Hondius, the cruise ship at the center of the deadly outbreak. According to public health officials, 18 passengers who disembarked the cruise ship on Sunday returned to the United States. Georgia Department of Public Health Communications Director Nancy Nydam said she could not provide information on whether the pair had tested positive for Hantavirus. The remaining two passengers were taken to Emory University's biocontainment unit. The patient in the Omaha, Nebraska, biocontainment unit tested positive before arriving back in the United States and is one of nine people worldwide who have tested positive in connection with the outbreak, according to the World Health Organization.

WHO investigators believe the outbreak stemmed from a Dutch couple on board the ship who came in close contact with wildlife carrying the virus before boarding the vessel. According to public health officials, at least two former passengers are quarantining at home in Georgia; three in California, where a fourth person, who was not a passenger but was exposed to an ill passenger aboard an airplane, is also in quarantine. Another former passenger is in quarantine at home in Arizona, according to Fox10 Phoenix and KOLD News 13. Most went to the University of Nebraska Medical Center, where one is in the center's biocontainment unit and 15 are in quarantine. CDC officials said the two were moved to preserve space at the Nebraska biocontainment unit.

The Nebraska patient is " doing well and not showing any symptoms." According to Emory, the patients sent to Atlanta are a couple, and one was showing symptoms. Symptoms can develop as long as six weeks after exposure. Health experts say the current outbreak poses little risk to the general public. Arizona Department of Health Services officials did not immediately respond to requests for information.