The final step in an outbreak investigation is to do something about it and tell people what you did, so to intervene and report. So, one of the best ways to respond to an outbreak if you can is to remove the exposure that caused the outbreak. So, this intervention has a long history going back to at least John Snow. So, after his investigation, John Snow presented his results to the Board of Guardians from St. James parish where the Broad Street water pump was. As a result of this work and his investigation, the Board of Guardians removed the handle from the Broad Street pump on September 7th, 1854 and then the epidemic quickly receded. Though it's worth noting that while this makes a great story, the epidemic may have been about to end anyway. So, if you look at this epidemic curve, you'll see that the number of fatal cases had been decreasing for many days by the time the pump handle was removed. So, the outbreak may have been going away anyway. Another common response to an outbreak is to recommend behavior change. So, on the left, we show an epidemic curve and you can see it follows our point-source pattern with a quick uptick then a slow fall, that's showing cases of E. coli associated with exposure to pork products. So, here in response, health officers demonstrated proper hand washing and environmental surface sanitation procedures. Identified other strategies the operators could use to reduce the likelihood of cross-contamination. That is they tried to change behaviors at food processing facilities to prevent a future outbreak. Then for many diseases one of the best responses is to treat or vaccinate cases. So, for instance here we're showing an outbreak of measles. The response was to do post-exposure prophylaxis with MMR vaccine, that's measles mumps or rubella vaccine or immunoglobulin for susceptible people who were exposed to cases. So, it's important to report what we've done. So, your report should cover all key elements in an outbreak investigation. So, all of the steps we've discussed in this module. The CDC's MMWR is an excellent source for seeing the elements of a good report. Every week there's many outbreaks reports there that follow a typical cause. Key sections of report are: the introduction and background, investigation and results, a characterization of the public health response, and some discussion to put it in the larger context of disease control. So, key points from this section is that no outbreak investigation is done until we intervene and report. We don't just want to know what happens, we want to do something about it. Interventions range from recommended changes, to procedures and policies, to an active response where we treat cases or perform prophylactic treatment. Report should clearly outline all the elements of an outbreak investigation and the public health response. So, as an exercise, think about the zoo outbreak that we investigated in the last section. Given what you found in terms of when people were likely exposed to the plague, what would you recommend for an intervention at the zoo to prevent future outbreaks? So, to summarize everything we've talked about in this module, in investigating outbreak we want to first establish a case definition by person, place, and time and actively find cases. That is answer the who of who's involved in the outbreak. Second, we want to build a line list of cases and use this to build epidemic curves and maps to characterize the outbreak in space and time, that is characterize when and where the cases are occurring. We didn't want to use clinical epidemiological and laboratory evidence to characterize the pathogen causing the outbreak. What is this an outbreak of? Then we want to use risk-factor study, define behaviors and exposures associated with the disease. In other words, determine why the outbreak is occurring. Finally, we want to recommend or perform interventions and report results. Take action to stop the outbreak. So, this concludes the module in identifying and investigating outbreaks. Thank you for your interest and attention.
