George Washington University PUBH 6003_Homework_Exercise 3_Briana_Evans. PH 6003 Graded Exercise 3 (Week 6): Outbreak Investigations Name _______Briana
... [Show More] Evans__________________ This exercise i s graded out of 50 possible points. Remember this is worth 10% of your total grade so strive for your best quality work! Please ask your lead about acceptable formats to be turned in. Generally typed answers are preferred. Write out answers so that they a clear and unambiguous and show your work for any calculations you are in doubt (this allows for partial credit). If you believe you had to make certain assumptions in order to answer a question state what those assumptions are. All work after the live session group work is to be strictly your own but you can still ask your instructor for clarifications on concepts or questions. Consider the following limited data. Answer each question using only the data given up to that point. 1. In August 1999, an “unusual cluster of cases of meningoencephalitis associated with muscle weakness was reported to the New York City Department of Health”. What is the first thing they needed to determine? (2pts) 2. What appears to be the “case definition” that was being used? Include all aspects that can be inferred from the above information. (3pts) 3. The first 8 patients identified had no apparent common exposure EXCEPT all patients had reportedly “engaged in outdoor activities (e.g., gardening)”. What might this suggest? (1pt) \ 4. “Active surveillance was implemented to identify patients hospitalized with viral encephalitis and meningitis. Cerebrospinal fluid, serum, and tissue specimens from patients with suspected cases PH 6003 Graded Exercise 3 (Week 6): Outbreak Investigations underwent serologic and viral testing for evidence of arboviral infection.” Why was “active surveillance” necessary? (2pts) 5. They found a total of 59 patients. Fill the attack rate, RR by characteristic (6pts) . 6. Calculate the overall attack rate (1 pt.) 7. Describe 2 patterns you can see from this data. (2pts) 8. Use the following data to create an epidemic curve: (4 pts) Cases of Disease Reported 9. What is your first impression about the type of outbreak going by the shape of the epi curve and why? (2pts) 10. How would this change if you learned that onset of illness was typically about a week from exposure (with a range of a few days to 2 weeks) and why? (2pts) 11. “The laboratory, clinical, and epidemiologic data indicated that the outbreak in New York City was most consistent with an outbreak of St. Louis encephalitis, and mosquito- control measures were instituted rapidly.” It was only later in the investigation that researchers identified the actual pathogen as West Nile Virus (WNV) which, unlike the St Louis encephalitis virus, can kill the avian reservoir hosts. It was found to be responsible for a concurrent epizootic outbreak killing substantial numbers of birds in the area. Why didn’t investigators wait until they knew for certain which virus it was? (2 pts) PH 6003 Graded Exercise 3 (Week 6): Outbreak Investigations The first part of this exercise was based on a paper in the New England Journal of Medicine, June 14, 2001 issue, titled “The Outbreak of West Nile Virus in the New York City Area in 1999” by Nash et al. They describe the first known outbreak of WNV in the Western Hemisphere. 12. Why was it important to go on and still identify the causative agent as WNV? (2pts) 13. The authors conclude “West Nile virus will most likely spread beyond the northeast and may cause sporadic cases or outbreaks of West Nile virus disease in other regions of the United States.” Why did they not believe it could be eradicated and would spread? (2 pts) For questions 14-16 consider these hypothetical reports made to the health department in each state and then determine if this would be an outbreak to immediately investigate. You will need to look for additional real information to answer teach question and give your source (it can just be the URL) 14. Ten cases of WNV are reported in Hawaii next year. (2 pts) 15. 100 cases of WNV are reported in Arizona over next summer. (2 pts) PH 6003 Graded Exercise 3 (Week 6): Outbreak Investigations 16. Twenty cases of WNV are reported in Illinois in next April (2pts). 17. In this first outbreak of WNV, 7 of the 59 cases were reported to have died of their illness. What was the case fatality rate (CFR)?(2pts) 18. Why is this CFR so much higher than what is now generally expected as the CFR of this infections? (2pts) 19. How would you describe WNV, using current information from the CDC or other appropriate sites, in terms of high, moderate or low*: a) virulence, b) pathogenicity and c) immunogenicity? Give some quantitative justification for each answer (6pts) don’t worry about exact cut offs for these categories – just a reasonable choice based on data. 20. To date there is no vaccine available for WNV, although there are some studies underway to develop one. Let us suppose a study of a potential vaccine was done on 150 individuals – all of whom test negative for any past exposure to WNV. A double blind randomized clinical trial is used to compare the vaccine to a placebo, with equal numbers in both groups. All individuals reside in the same area and WNV is endemic to this area. 42 of those who received the placebo contract WNV (indicated by regular blood tests), but among those who receive the vaccine only 2 do at the end of 1 year of follow-up. What is the vaccine efficacy? (3pts) Add [Show Less]