Cruise Ship Epidemics
Deception In These Outbreak Statistic
Understanding Why These Numbers Are Low
NOTE: Cases reported in this category only reflect those reported to the infirmary. Many passengers do not seek medical care aboard a ship, due to the high expense.
In order to really understand what these statistic mean, you have to understand how the CDC reporting works.
The CDC gets reports only when 3% of the passengers aboard a ship have contracted a communicable disease. This means, that if the cruises before and after that reportable incident, are less, they normally will not be seen on the CDC web site. However, indications that they existed, do quite frequently show up in reports.
For example, let's look at a cruise ship reporting 8% of passengers ill out of 3,000 on cruise #3. On cruise #1 the percentage was likely around 1%. Then, on cruise #2 the percentage escalated to 2%. We don't know these figures, because the ship doesn't have to report until the number of ill reaches 3%.
The CDC notification was made on cruise #3, when the percentage jumped to 8%. After disinfecting the ship with CDC supervision, sometimes after the CDC has advised the ship to stay in port to thoroughly clean the vessel, notes are seen in the CDC report, at the very bottom.
Those notes say in one case, "Holland America Line, Ryndam 01/13/2005 – 01/29/2005). The vessel sailed from San Diego, CA to Ft. Lauderdale, FL. At the end of the voyage, medical staff reported that 272 of 1223 (22.2%) passengers and 37 of 574 (6.4%) crew were ill. Stool specimens were collected and tested positive for norovirus. Medical staff continued to monitor gastrointestinal illness cases; by the following voyage the number of reported cases returned to expected levels."
At this point, the CDC is out of the picture. What happens on that ship from that point on, is between the passengers, crew and ship management from that point on, unless the numbers escalate again to reportable levels.
From we can expect, cruise #4 might be back to 2%. Then, cruise #5 at 1%, and perhaps even cruise #6 at 1/2%. This would be typical, to see the outbreak over five to six cruises.
We, the public only see the one outbreak and think that only 240 passengers were affected. Using the example above, let's look at the real numbers.
Cruise #1 - 1% of 3000 = 30
Cruise #2 - 2% of 3000 = 60
Cruise #3 - 8% of 3000 = 240
Cruise #4 - 2% of 3000 = 60
Cruise #5 - 1% of 3000 = 30
Cruise #6 - .05% of 3000 = 15
Total In Outbreak = 435
Even then, these numbers are the tip of the iceberg. Thirty sick people do not just drop into a cruise ship, all at one time. From the first count on, passengers becoming ill aboard are the result of the crew failing to perform their duties correctly, and perhaps, being sick themselves, reinfecting the ship.
Since all the first 30 passengers disembarked, taking their germ infested bodies with them, all that was left was the crew. If there is a continue outbreak on cruise #2 through cruise #6, this is a direct reflection on the crew and slack management aboard.
How can we know for sure how many were sick, and how long the outbreak lasted? We can't. But, if the reported numbers are high, you know for sure this was not the first cruise people were ill. The numbers typically escalate, peak, then decline over a period of weeks or months.
On average, once a year, we see the CDC reporting two or three consecutive cruise with reportable outbreaks. With these outbreak, we can assume the outbreak really lasted five to nine consecutive cruises.
Such might be the case on the Queen Elizabeth 2 in 2004. The CDC shows two outbreaks, the first on the cruise January 5 through January 19th. Then again, the ship is shown for an outbreak February 17th through March 1st.
The first outbreak there were 29 passengers and 46 crew sick for a total of 75 reported cases. This particular incidents shows, that the problem most likely originated in the crew. Were 46 crew sudden ill? Not likely. This probably escalated over one or two cruises before the reportable cruise.
The second outbreak, the number of passengers ill had increase to 82 and the number of crew had declined to 24 for a total of 106 cases.
Because the crew numbers were predominate in the first outbreak, it is highly unlikely these two outbreaks are unrelated. Though we will never know the numbers, we can assume a reasonable progression scale as follows:
Cruise #1 - December 8 to December 22 - 25 estimated cases
Cruise #2 - December 22 to January 5 - 55 estimated cases
Cruise #3 - January 5 to January 19 - 75 reported cases
Cruise #4 - January 19 to February 2 - 85 estimated cases
Cruise #5 - February 2 to February 16 - 95 estimated cases
Cruise #6 - February 16 to March 1 - 106 reported cases
Cruise #7 - March 1 to March 15 - 55 estimated cases
Cruise #8 - March 15 to March 29 - 25 estimated cases
Reported cases = 181
Estimated cases + reported cases = 521
Note that the forward progression building towards a reportable amount grows only slightly until peaking. Once the numbers peak, there is CDC intervention, action taken to stop the outbreak and the numbers decrease rapidly. In actual practice, this outbreak likely started with a single case back in mid November and lasted until late April, a period of five months.
Where an outbreak is attributed to food, such as Salmonella from shrimp, the progression forward is less than with a typical Norovirus outbreak. There is a sudden number of those who become ill after eating the contaminated or incorrectly stored/prepared food.
Then, the numbers decline over the next few cruises, or they then evolve into Norovirus, due to poor hygiene habits of those who had diarrhea from the Salmonella, then the numbers decline.
In any case, the numbers made public, due to the reporting regulations, are weak and watered down at best. The primary reason for this is money.
In the CDC letter sent to a Cruise Bruise visitor, and then forwarded on to us, the CDC indicates that there are five ships a week with mass illness aboard. though because the numbers are not at reportable levels, the public is not privy to the information. They simply to not have the money, nor do they want to spend the money, to change and then enforce regulations.
If ships were to report every visit to the infirmary, both passenger and crew, where GI illnesses type symptoms were present, representing a potential communicable disease, these numbers would skyrocket without CDC intervention. If the CDC was to intervene earlier, outbreaks could be caught earlier and the annual numbers would decline substantially.
The CDC advises ships, that they only have to advise boarding passengers of an outbreak on the previous cruise IF the numbers were CDC reportable at the 3% or more level.
The final thing to keep in consideration is the fact that many people do not go to the infirmary for a "stomach bug", just as they don't at home. The cost of visiting the infirmary aboard is typically $500 without serious complications, such as receiving an IV to reverse dehydration.
If the numbers were known, as to how many people were actually sick, they would rise. We know that, because in severe outbreaks, the ship has reported one number of those affected, but after the CDC boarded the ship and sent out questionnaires to find how many were actually sick and with what symptoms, the numbers rise dramatically. Since this is not done during average outbreaks, the true numbers are not document, nor made public.
