Cruise ships are a hard environment for a contagious gut infection to be
ignored in: a fixed population, shared food, shared bathrooms, and no way to
send anyone home. CDC's Vessel Sanitation Program (VSP) therefore runs
continuous surveillance, and the whole system rests on counting.
The case definition
A reportable case of acute gastroenteritis (AGE) is:
- Three or more loose stools within a 24-hour period, or **more than is
normal for that person**
OR
- Vomiting along with one of: diarrhoea, muscle ache, headache, abdominal
cramp, or fever
The "or more than is normal for that person" clause is doing real work — a
fixed threshold would both miss and over-count, depending on the individual.
The chain of reporting
| Who | What they do |
|---|---|
| Passengers and crew | Tell ship medical staff they are sick |
| Medical staff | Enter reportable cases in the log |
| Ships | Required to log and report numbers for passengers and crew, and to keep a list of everyone issued antidiarrhoeal medication |
| VSP | Receives reports at required times, and monitors for patterns |
The antidiarrhoeal list is the clever part. It catches the people who never
report being ill but quietly ask for something for it — a self-reported count
would miss exactly those.
The two thresholds
| 2% of passengers or crew ill, or an unusual pattern or characteristic | VSP provides support and technical assistance |
| 3% of passengers or crew ill | Considered an outbreak |
Two percent is not a crisis. It is the point at which help arrives before one.
What the data is for
VSP monitors reports to determine if a high number of people are sick,
find unusual cases, support the cruise line and crew as they respond,
and analyse illness patterns over time.
AGE is highly contagious and can be caused by viruses — norovirus
above all — or by bacteria or parasites, including E. coli and
Salmonella.
Source: Centers for Disease Control and Prevention.
许可协议： CC0 1.0（公有领域） · 改编自 www.cdc.gov
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