Running Head EPIDEMIOLOGY

Rubella



Rubella

Introduction

In epidemiology, a cohort design or cohort study is a non-experimental study design that involves comparing the occurrence of epidemiologic aspects of or condition in two or more groups or cohorts of people that differ on a certain characteristic, risk factor, or exposure. The epidemiologic aspect of disease, state, or condition under study is often referred to as the outcome, whereas the characteristic, risk factor, or exposure is often referred to as the exposure. A cohort study is one of two principal types of non-experimental study designs used to study the causes of disease. The other is the case control design, in which cases of the disease under study are compared with respect to their past exposure with a similar group of individuals who do not have the disease.

The virus that causes rubella is a ribonucleic acid virus and a member of the Togaviridae family, which also includes the arboviruses. The rubella virus, however, is not related serologically to arboviruses or any other known viruses. Rubella is spread either by the direct contact with nasopharyngeal secretions of an infected individual or through droplets. Congenital infections in infants result from trans-placental spread of virus associated with maternal vermeil during a primary infection.

Discussion

Cohort is the term used in epidemiology to refer to a group of individuals who share a common characteristic; for example, they may all belong to the same ethnic or age group or be exposed to the same risk factor. The cohort study is a relatively recent innovation which identifies and explains the natural history of the infectious disease through the epidemiology aspect, which may include all people, diagnosed with a precursor or an early form of the disease and then followed up as their disease progressed. (Beksinska, Rees and McIntyre, 1999)

Epidemiology and Transmission

Rubella occurs throughout the world, hut the epidemiology varies globally. In temperate climates, the peak incidence for infection is the late winter and spring. Rubella remains prevalent in many areas of the world in which the rubella vaccine is not used. In the United States and other countries where the vaccine has been given routinely since the early 1970s, the epidemiology of rubella has changed dramatically. (Lilienfeld, 1980)Epidemics of rubella, which occurred in 6 to 9 year cycles prior to vaccine use, have been disrupted and endemic rubella has been almost eradicated in the United States. A 99% reduction in reported cases of rubella and the congenital rubella syndrome (CRS) occurred in the United States between 1965, when the last epidemic occurred, and 1998. With the exception of 1998, there were fewer than 300 reported cases of rubella each year in the United States between 1992 and 1999. (Belay, 1999)

The demographic characteristics of individuals with rubella reported to the Centers for Disease Control and Prevention also changed significantly during the decade of the 1990s. During this decade, rubella occurred more commonly in older individuals than children. Children younger than 15 years of age accounted for only 11% of the cases in 1996 compared ...