Amber McAllister
Principles of Epidemiology Anne McHugh August 14, 2022
Final Project
Salmonellosis, more commonly known as Salmonella, is a gastrointestinal illness caused by
bacteria. The symptoms can include sudden onset of headache, abdominal pain, diarrhea (which
may be bloody), nausea, and sometimes vomiting. Fever is almost always present. The illness
typically lasts for 5-7 days and usually does not require treatment unless the patient becomes
severely dehydrated or the infection spreads from the intestines. In the immunocompromised
host or an overwhelming infection in a normal host, Salmonella may spread to the blood stream
and other body sites, and can cause death unless treated promptly with antibiotics. (Stehr-Green,
2016) The bacteria live in the intestinal tracts of their hosts which can be humans or animals. It
can be transmitted to humans by eating foods that are contaminated with animal fecal matter.
Some of the risk factors in transmitting the bacteria are improper hand washing while handling
raw meats and eggs or after using the restroom. However, studies have shown that the number
one risk factor for humans is the consumption of raw or undercooked eggs.
This has been proven in the case study provided, by researching eggs and where they came from.
and how they were handled prior to consumption. It was found that non-sanitized eggs that were
consumed from unsanitary farms were more likely to contract Salmonella. Table 1 from the case
study, it is shown from 1995-97, 257 laboratory-confirmed cases of S. Enteritidis infection were
reported in Trinidad and Tobago. In those years approximately, 86 cases were reported each year
for an annual incidence of 6.8 per 100,000 people in the population. In general, the geographic
distribution of patients with S. Enteritidis infection reflected population distributions on the two
islands. The largest numbers of cases were reported from the most populous counties of St.
George and Victoria. An average of 4 people died each year from salmonella infection. (Stehr-
Green, 2016) Breaking this information down to just formulas would be equal to:
Incidence Rate= (86 cases/1,265,000population) *100,000= 6.79, rounded to 6.8
Prevalence= (1097cases in study/1,265,000 population) = 86.7 per 100,000 people
Morality = (40/ 1,265,000) * 100,000= 3.16, rounded to 4
In table 2 of the case study, the odds ratio can be determined as the highest at 18.9 being raw or
undercooked eggs and the lowest at 0.03 for refrigerated eggs at home. There were some other
odds being factored in such as shells being eaten coming in at 8.8 which is the second highest
odd therefore supporting the case study that the common exposure to unsanitary eggs was the
leading cause of the Salmonella outbreak. An odds ratio (OR) is another measure of association
that quantifies the relationship between an exposure with two categories and health outcome.
Referring to the four cells in Table 3.15, the odds ratio is calculated as
Odds ratio= (a/b)(c/d)= ad/bc
where
a = number of persons exposed and with disease b = number of persons exposed but without disease c