Case study on Salmonella Outbreaks in the U.S.

Every year, approximately 42,000 cases of salmonellosis are reported in the United States. Because many milder cases are not diagnosed or reported, the actual number of infections may be twenty-nine or more times greater. It is estimated that approximately 400 persons die each year with acute salmonellosis. A small number of persons with Salmonella develop pain in their joints, irritation of the eyes, and painful urination. This is called reactive arthritis. It can last for months or years, and can lead to chronic arthritis which is difficult to treat. Antibiotic treatment does not make a difference in whether or not the person develops arthritis. (CDC, 2013)

1) Using your OWN WORDS describe the full Chain of Infection for Salmonella. Cite your references:

a) Agent(s):
b) Reservoir(s):
c) Exit/Transmission/Entry:
d) Host Susceptibility:

2) Find and include the most current CASE DEFINITION for Salmonellosis. Cite your source(s):

3) Use the attached source, The MMWR Notifiable Diseases – U.S., 2011 (http://www.cdc.gov/mmwr/PDF/wk/mm6053.pdf), to answer these problems about the descriptive epidemiology of Salmonella morbidity in the US.  Support your answers by including some data comparisons from this source.

a) Is it seasonal?  If so, what is its seasonality?
b) Is it geographically specific? (Refer to US regions, not sates)
c) What is the term trend (2004 -2011) in Reported Cases per year?

4) There are currently two active US outbreaks of Salmonella involving live poultry. Much of the exposure is coming from backyard pets and small suburban flocks of chickens and ducks. To investigate the source of salmonella in these livestock, the CDC has been randomly testing chicks and ducklings at the sources for these livestock: farm stores and mail-order livestock suppliers. Twelve suppliers were randomly selected in each category and 100 chicks or ducklings were tested per site.  Here are the data for the number of positive tests per 100 livestock tested per supplier:

Mail-Order: 5, 7, 6, 3, 6, 4, 5, 2, 6, 8, 6, 7
Farm Stores: 8, 3, 6, 7, 3, 4, 8, 7, 3, 2, 8, 6

a) Create a Frequency Table for BOTHsources

b) Compute, compare, and interpret the following for BOTHsources.

You MUST show your full computations for credit:

• Meanand Mode of infected livestock   
• Confidence Intervals
• For which source are we most confident that our tests results can be inferred to similar sources? How do you know?
• Toward which sourceshould the CDC direct itsregulatory efforts? Why?