The cruise ship Balmoral is prepared prior to boarding of passengers going on the Titanic Memorial Cruise in Southampton, England April 8, 2012. An outbreak of the norovirus stomach bug has sickened 160 people aboard a Fred Olsen Cruise Lines ship docked at Norfolk, Virginia, U.S. health officials and the company said on Friday. The norovirus outbreak took place aboard the Britain-based line's Balmoral during a transatlantic cruise, the Centers for Disease Control and Prevention (CDC) said in a statement. REUTERS/Chris Helgren/File Photo 

A paramedic dressed in protective attire stands in front of the ship, the Bellriva, in Wiesbaden December 8, 2012. The Bellriva has been quarantined after at least 30 passengers were found to be suffering from diarrhoea and vomiting. Authorities believed it is caused by the Norovirus, a virus that is spread from person-to-person and causes flu-like symptoms. REUTERS/Lisi Niesner (GERMANY - Tags: HEALTH SOCIETY) 

A general view of the ship, the Bellriva, is pictured in Wiesbaden December 8, 2012. The Bellriva has been quarantined after at least 30 passengers were found to be suffering from diarrhoea and vomiting. Authorities believed it is caused by the Norovirus, a virus that is spread from person-to-person and causes flu-like symptoms. REUTERS/Lisi Niesner (GERMANY - Tags: HEALTH SOCIETY TRANSPORT) 

Paramedics dressed in protective attire are reflected in a window of the ship, the Bellriva, in Wiesbaden December 8, 2012. The Bellriva has been quarantined after at least 30 passengers were found to be suffering from diarrhoea and vomiting. Authorities believed it is caused by the Norovirus, a virus that is spread from person-to-person and causes flu-like symptoms. REUTERS/Lisi Niesner (GERMANY - Tags: HEALTH SOCIETY) 

A paramedic dressed in protective attire holds a box next to the ship, the Bellriva, in Wiesbaden December 8, 2012. The Bellriva has been quarantined after at least 30 passengers were found to be suffering from diarrhoea and vomiting. Authorities believed it is caused by the Norovirus, a virus that is spread from person-to-person and causes flu-like symptoms. REUTERS/Lisi Niesner (GERMANY - Tags: HEALTH SOCIETY) 

Seagulls fly above the ship, the Bellriva, in Wiesbaden December 8, 2012. The Bellriva has been quarantined after at least 30 passengers were found to be suffering from diarrhoea and vomiting. Authorities believed it is caused by the Norovirus, a virus that is spread from person-to-person and causes flu-like symptoms. REUTERS/Lisi Niesner (GERMANY - Tags: HEALTH SOCIETY) 

Paramedics dressed in protective attire enter the ship, the Bellriva, in Wiesbaden December 8, 2012. The Bellriva has been quarantined after at least 30 passengers were found to be suffering from diarrhoea and vomiting. Authorities believed it is caused by the Norovirus, a virus that is spread from person-to-person and causes flu-like symptoms. REUTERS/Lisi Niesner (GERMANY - Tags: HEALTH SOCIETY) 

Paramedics dressed in protective attire stand in front of the ship, the Bellriva, in Wiesbaden December 8, 2012. The Bellriva has been quarantined after at least 30 passengers were found to be suffering from diarrhoea and vomiting. Authorities believed it is caused by the Norovirus, a virus that is spread from person-to-person and causes flu-like symptoms. REUTERS/Lisi Niesner (GERMANY - Tags: HEALTH SOCIETY) 

Paramedics dressed in protective attire walk in front of the ship, the Bellriva, in Wiesbaden December 8, 2012. The Bellriva has been quarantined after at least 30 passengers were found to be suffering from diarrhoea and vomiting. Authorities believed it is caused by the Norovirus, a virus that is spread from person-to-person and causes flu-like symptoms. REUTERS/Lisi Niesner (GERMANY - Tags: HEALTH SOCIETY) 

Paramedics, dressed in protective attire, leave the ship, the Bellriva, in Wiesbaden December 8, 2012. The Bellriva has been quarantined after at least 30 passengers were found to be suffering from diarrhoea and vomiting. Authorities assume it is caused by the Norovirus, a virus that is spread person-to-person and causes flu-like symptoms. REUTERS/Lisi Niesner (GERMANY - Tags: HEALTH) 

A Red Cross paramedic in full protection gear leaves the 'Lady Anne' cruise ship in Boppard November 26, 2008. The Lady Anne has been docked in quarantine at the town of Boppard after 39 of the 100 passengers, who were on a cruise of the Rhine river, were found to be suffering from the Novovirus, a virus that is spread person-to-person and causes flu-like symptoms. REUTERS/Wolfgang Rattay (GERMANY) 

An elderly woman leaves the Rhine cruising ship 'Lady Anne' together with two Red Cross paramedics in full protection gear in Boppard November 26, 2008. The 'Lady Anne' has been docked in quarantine at the town of Boppard after 39 of the 100 passengers, who were on a cruise of the Rhine river, were found to be suffering from the Norovirus, a virus that is spread person-to-person and causes flu-like symptoms. REUTERS/Wolfgang Rattay (GERMANY)