Case Studies for Fundamentals in Epidemiology

The objective of Case Studies for Fundamentals of Epidemiology is the collection of cases to illustrate the principles taught in Fundamentals of Epidemiology, a Johns Hopkins Bloomberg School of Public Health course with content available via JHSPH OpenCourseWare.

Fundamentals in Epidemiology Course Description
Fundamentals of Epidemiology introduces the basic concepts of epidemiology and biostatistics as applied to public health problems. Emphasis is placed on the principles and methods of epidemiologic investigation, appropriate summaries and displays of data, and the use of classical statistical approaches to describe the health of populations. Topics include the dynamic behavior of disease; usage of rates, ratios and proportions; methods of direct and indirect adjustment, and clinical life table which measures and describes the extent of disease problems. Various epidemiologic study designs for investigating associations between risk factors and disease outcomes are also introduced, culminating with criteria for causal inferences. The application of these disciplines in the areas of health services, screening, genetics, and environment policy are presented. The influence of epidemiology and biostatistics on legal and ethical issues are also discussed.

Case Studies
Case studies are illustrative examples of the epidemiologic concepts taught within Fundamentals of Epidemiology. The course instructors are particularly interested in epidemiologic studies conducted in West Asia and the Arabian Peninsula and published in peer-reviewed journals or as reports to organizations.

The study types include outbreak investigations, clinical trials, cohort (longitudinal) studies, and case-control studies.

Please contribute case studies by editing the corresponding sections below.

Outbreak Investigations
Edit this section to contribute a case study that illustrates the characteristics of properly designed outbreak investigations.

Measles outbreak in Qassim, Saudi Arabia, 2007
This case study illustrates the principles taught in Lecture 2: Epidemiologic Investigation.

Despite high vaccination rates in this population, a measles outbreak occurred from January 2007 through August 2007 in Qassim, Saudi Arabia. An investigation was conducted to describe the epidemiology of outbreak, and an audit of the Primary Health Care team's control measures was performed according to WHO standards. Of 230 cases reported, 37.8% of patients were 0 to 4 years old. Children aged 6 to 11 months accounted for 51.7% of cases among the 0- to 4-year-old age group. The performance indicator targets of 80% for outbreak control measures were achieved regarding investigation of cases within 48 hours, and blood sample extraction was within the optimal period. However, 66.8% cases reported within 48 hours of rash onset and only 16.4% of laboratory test results were received within 7 days of receipt of the specimen in laboratory. Investigators concluded that this outbreak demonstrates increased susceptibility of unvaccinated children aged 6 to 11 months. Prevention of future outbreaks requires community awareness, review of the measles vaccination schedule, enhanced measles surveillance, and a "catch-up" mass immunization campaign to interrupt chains of transmission.

Summarized from Jahan S, Al Saigul AM, Abu Baker MA, Alataya AO, Hamed SA. Measles outbreak in Qassim, Saudi Arabia 2007: epidemiology and evaluation of outbreak response. J Public Health (Oxf). 2008 Aug 20. [Epub ahead of print] Full Text Article

Clinical Trials
Edit this section to contribute a case study that illustrates the characteristics of properly designed clinical trials.

Nebulized hypertonic saline in the treatment of viral bronchiolitis in infants.
This case study illustrates the principles taught in Lecture 12: Randomized Clinical Trials.

This purpose of this prospective, randomized, double-blinded, controlled, multicenter trial was to investigate the use of nebulized 3% hypertonic saline (HS) to treat viral bronchiolitis in moderately ill hospitalized infants. Over the course of three bronchiolitis seasons (December 2003 to May 2006), the authors recruited 96 infants (mean age, 4.7 months; range, 0.3 to 18 months) from three regional pediatric centers (Sheikh Khalifa Medical City, Abu Dhabi, United Arab Emirates; Victoria General Hospital, Victoria, British Columbia, Canada; and Kingston General Hospital, Kingston, Ontario, Canada) admitted for treatment of viral bronchiolitis. Patients were randomized in a double-blind fashion; the treatment group received repeated doses of nebulized 3% HS, and the control group received 0.9% normal saline (NS). After randomization, patients in both groups received routine therapy ordered by the attending physician, who was blinded to the study treatment. The principal outcome measure was hospital length of stay (LOS). On an intention-to-treat basis, the infants assigned to the HS group had a clinically relevant 26% reduction in LOS to 2.6 +/- 1.9 days, compared with 3.5 +/- 2.9 days in the NS group (P = 0.05). The treatment was well tolerated, and there were no adverse effects attributable to the use of HS. The authors conclude that the use of nebulized 3% HS is a safe, inexpensive, and effective treatment for infants hospitalized with moderately severe viral bronchiolitis.

Summarized from Kuzik BA, Al-Qadhi SA, Kent S, Flavin MP, Hopman W, Hotte S, Gander S. Hypertonic saline in the treatment of viral bronchiolitis in infants. J Pediatr 2007;151:235-237. Full Text Article

Cohort (Longitudinal) Studies
Edit this section to contribute a case study that illustrates the characteristics of properly designed cohort studies.

Clinical and immunological manifestations in 151 SLE patients living in Dubai
This case study illustrates the principles taught in Lecture 13: Cohort Studies.

The authors studied the clinical and immunological manifestations of systemic lupus erythematosus (SLE) in a cohort of 151 patients attending the Rheumatology Clinic in Dubai Hospital between January 2002 and January 2007 to gain better understanding of SLE in Dubai. The female to male ratio was 20.5:1, and the mean age was 35.5 years (0.9). The mean age at disease onset was 28.9 years (0.8), and mean disease duration 6.7 years (0.4). The 5-year survival rate in our cohort was 94%. The most commone clinical manifestations were arthritis (88%), haematological abnormalities (61.6%), and malar rash (60.3%). Leucopenia, fever, hair loss, and proteinuria were also observed in approximately 50% of the patients. Anaemia was found in 44.3% of the cohort, but haemolytic anaemia was found in only 9.9%. Photosensitive rash was seen in 43% of patients, and 30.5 and 27.2% of the cohort had serositis and mouth ulcers, respectively. Vasculitis was observed in 19.2% of patients, and neuropsychiatric manifestations (15.9%), discoid lupus lesions (12.6%), and brain infarcts (13.2%) were infrequent. Subacute cutaneous lupus (6%) was also uncommon. Anti-nuclear antibodies were detected in 98%, anti-double stranded DNA antibodies in 88.7%, anti-Sm antibodies in 19.7%, anti-RNP in 40.4%, anti-Ro antibodies in 52.3%, and anti-La antibodies in 19.8%. Anti-cardiolipin IgM and IgG were detected in 25.3 and 22.4%, respectively. This study suggests that the clinical features of Arabs with SLE residing in Dubai are similar to the clinical features of their counterparts in other Arab countries and in Western countries. The high prevalence of positive anti-Ro antibodies among our Arab patients probably reflects a characteristic that is commonly seen in SLE patients of Middle Eastern origin.

Summarized from AlSaleh J, Jassim V, ElSayed M, Saleh N, Harb D: Clinical and immunological manifestations in 151 SLE patients living in Dubai. Lupus 2008; 17; 62. Full Text Article

Case-Control Studies
Edit this section to contribute a case study that illustrates the characteristics of properly designed case-control studies.

Clinical predictors of intractable childhood epilepsy
This case study illustrates the principles taught in Lecture 14: Case-Control Studies.

This objective of this study was to determine the clinical, electroencephalographic, and radiological factors associated with medically intractable seizures in children in the Al Ain Medical District in the United Arab Emirates. The authors used a prospective case-control study of children referred to pediatric neurology and neurodevelopmental clinics at Tawam and Al Ain University Hospitals. Data from 55 children with intractable epilepsy were compared with 50 children who responded well to treatment with antiepileptic drugs and who were seizure-free for at least 2 years. Factors found to be significantly more common in the study group included onset before 1 year of age, high seizure frequency at onset, positive history of neonatal seizures, developmental delay and status epilepticus, neurological deficits, and abnormal brain imaging results. Furthermore, symptomatic localization-related epilepsy was found to be more common among children with intractable epilepsy than in the control group. The authors conclude that children presenting with idiopathic localization-related and generalized epilepsy syndromes with few seizures at onset and with no neurological deficits tend to have a relatively good prognosis.

Summarized from Gururaj A, Sztriha L, Hertecant J, Eapen V. Clinical predictors of intractable childhood epilepsy. J Psychosom Res. 2006 Sep;61(3):343-7. Full Text Article

Mesures of Morbidity and Mortality
Edit this section to contribute a case study that illustrates the characteristics of properly designed measures of morbidity and mortality.

Seasonality in pulmonary tuberculosis among migrant workers entering Kuwait.
Background: There is paucity of data on seasonal variation in pulmonary tuberculosis (TB) in developing countries contrary to recognized seasonality in the TB notification in western societies. This study examined the seasonal pattern in TB diagnosis among migrant workers from developing countries entering Kuwait. Methods: Monthly aggregates of TB diagnosis results for consecutive migrants tested between January I, 1997 and December 31, 2006 were analyzed. We assessed the amplitude (α) of the sinusoidal oscillation and the time at which maximum (θ°) TB cases were detected using Edwards' test. The adequacy of the hypothesized sinusoidal curve was assessed by χ2 goodness-of-fit test. Results: During the 10 year study period, the proportion (per 100,000) of pulmonary TB cases among the migrants was 198 (4608/2328582), (95% confidence interval: 192 – 204). The adjusted mean monthly number of pulmonary TB cases was 384. Based on the observed seasonal pattern in the data, the maximum number of TB cases was expected during the last week of April (θ° = 112°; P < 0.001). The amplitude (± se) (α = 0.204 ± 0.04) of simple harmonic curve showed 20.4% difference from the mean to maximum TB cases. The peak to low ratio of adjusted number of TB cases was 1.51 (95% CI: 1.39 – 1.65). The χ2 goodness-of-test revealed that there was no significant (P > 0.1) departure of observed frequencies from the fitted simple harmonic curve. Seasonal component explained 55% of the total variation in the proportions of TB cases (100,000) among the migrants. Conclusion: This regularity of peak seasonality in TB case detection may prove useful to institute measures that warrant a better attendance of migrants. Public health authorities may consider re-allocation of resources in the period of peak seasonality to minimize the risk of Mycobacterium tuberculosis infection to close contacts in this and comparable settings in the region having similar influx of immigrants from high TB burden countries. Epidemiological surveillance for the TB risk in the migrants in subsequent years and required chemotherapy of detected cases may contribute in global efforts to control this public health menace.

Abstract copied from Akhtar S, Mohammad HG. Seasonality in pulmonary tuberculosis among migrant workers entering Kuwait. BMC Infect Dis. 2008;8:3. This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Full Text Article