Health regulators are still investigating the early January
outbreak of gastrointestinal illness on the Oasis of the Seas, one of the
largest on a cruise ship in the past 10 years.
Paradoxically, it arrived on the heels of 2018, which saw
the lowest number of onboard outbreaks in at least 17 years.
According to the U.S. Centers for Disease Control, 561
passengers were treated earlier this month for stomach flu over the course of a
cruise from Port Canaveral, which was shortened from seven days to six because
of the outbreak.
The number of those treated amounted to 8.9% of the passengers
on the ship. Authorities in Jamaica advised Royal Caribbean International not
to disembark passengers on a port call in Falmouth, and the ship's captain made
the decision to cancel a call at the next port, Cancun, and return home.
The severity of the attack prompted Royal to issue a full
refund to all 6,285 passengers onboard, a rarity for voyages that suffer
outbreaks.
Cmdr. Aimee Treffiletti, chief of the federal Vessel
Sanitation Program, which oversees outbreak response on cruise ships, was reluctant
to draw conclusions about why the outbreak was so large until the cause is
known.
"It's difficult at this point in time to be able to
say, because we haven't confirmed it was norovirus," Treffiletti said.
Norovirus, the cause of most gastrointestinal illness at
sea, is an easily spread microbe that is also the cause of many outbreaks on
land. It produces one to three days of vomiting and diarrhea but is not fatal.
It was the source of the largest illness outbreak at sea in
the past 10 years, a 2014 cruise from Bayonne, N.J., on which 634 people fell
ill. That cruise aboard the Explorer of the Seas was also operated by Royal
Caribbean.
In a 10-day period in January 2014, the outbreak affected
20.6% of the passengers on the ship. Royal did not end that cruise early, but
embarkation for the next voyage was delayed for disinfection and cleaning.
In that case, passengers got a 50% refund of their fare and
a 50% credit toward a future cruise.
Royal Caribbean did not comment on the reasons for issuing a
full refund on the Oasis. But in a statement, it said cutting short the cruise
was "the right thing to do to get everyone home early rather than have
guests worry about their health."
The massive outbreak on the Oasis is especially confounding
in light of the decline in such illness on cruise ships in 2018. Last year,
fewer people fell sick in outbreaks recorded on 10 ships than got ill on the
single voyage of the Oasis.
Only 547 passengers fell ill in the 2018 outbreaks, the
fewest since at least 2002, when a mutation in the virus led to a new strain
that sent outbreaks on cruise ships soaring for several years.
Notably, only one of the 10 outbreaks caused more than 100
passengers to get sick last year.
In a statement, the Vessel Sanitation Program, part of the
U.S. Centers for Disease Control, said fewer and less severe outbreaks in 2018
were likely the result of several factors.
One was earlier detection of illness. When sick passengers
are spotted by crew members, or if passengers volunteer their illness early in
the cruise instead of waiting, procedures for cleaning the vessel and
quarantining the ill work better.
Another factor cited by the CDC was "cruise industry
diligence" in developing and implementing outbreak prevention and control
plans. In 2016, CLIA formulated its "Sample Outbreak Prevention and
Response Plan" for members. It was particularly useful for smaller or new
cruise lines that hadn't previously adopted protocols.
In recent years, all cruise lines have required passengers
to complete a health form upon boarding or acknowledge in some way that they
are not suffering symptoms that could be caused by norovirus.
Some cruise lines do not allow passengers to serve
themselves from the buffet, at least in the initial days of the cruise.
Hand sanitizers are omnipresent in areas where food is
served. In designing new ships, cruise lines are also building hand-washing
stations with running water and soap at the entrances to buffet restaurants.
Over the years, cruise lines have also homed in on more effective
disinfection and cleaning agents for norovirus and have refined their methods
for interior cleaning after an outbreak occurs.
All those responses have contributed to a gradual decline in
outbreaks over the past 15 years, the CDC said. With the exception of 2012, the
agency said, "The rate of acute gastroenteritis illness on cruise ships
has decreased over time, as has the number and severity of outbreaks by year."