Outbreak Investigation
An unexpected rise in the number of cases of a particular identified or unidentified
disease alerts public health officials to respond to the situation through focused
investigation. Public health departments record patterns of diseases all year as part
of their surveillance. Epidemiological investigations conducted to identify the
causes of outbreak have led to the discovery of many new microorganisms. Epidemiological
studies on influenza have helped us to understand whether or not vaccination
programs are effective. Designated preventive measures to contain a disease
need to be reviewed continuously because of the changing patterns of some diseases.
The outcomes of such outbreak investigations should be communicated to
both the public and healthcare professionals throughout the world.
Because of rising fears of pandemics among healthcare professionals, the incidences
of cases are sometimes over-reported. The epidemiologist role in such situations
is a difficult one, because he or she has to collaborate with other teams to identify
the most common symptoms that the disease presents. Laboratory, genetic, and molecular
tools help to identify the disease-causing organism from various specimens
obtained from infected individuals. The accurate description of cases and identification
of a specific diagnostic tool can result in confirmation of the disease. Surveys can
then be designed to gather information from infected and exposed individuals. These
data are used to construct an epidemic curve from which the incubation period can be
calculated. Descriptive data can define certain characteristics of the disease (e.g., age
group and gender affected). The patterns of exposure to the source (continuous,
propagated, or intermittent) can be identified. After preliminary investigation, the
next step is to identify the source and transmission methods of the disease. A hypothesis
is then constructed and tested in the field by designing an appropriate study (casecontrol,
cohort, or survey study) to identify the source of infection. An environmental
investigation is also an important component to identify disease transmission pathways.
(Outbreak investigation involves the epidemiological triad: the study of host,
agent, and environment.) Preventive and therapeutic measures are designed to treat
infected individuals and also to break the transmission pathways. The information is
disseminated to healthcare professionals, and diagnostic tools are made available on a
large scale. Prevention measures involving vaccination involve complex research studies
and surveillance for any adverse effects of the vaccination.