Adjusted Rate. Any rate that has been mathematically transformed to eliminate the influence of one or more variables—most
Agent. An organism, substance, or force whose excess presence or relative absence is necessary for a particular disease to
Bed-Disability Days. Days on which one stays in bed due to illness.
Confounding. A situation in which the effects of two variables are not separable.
Crude Rate. Summary rate based on the actual number of events in a total population over a given period of time.
Disability. Any restriction or lack of ability to perform an activity in the manner or within the range considered normal
for human beings.
Epidemiology. The science that studies the distribution and determinants of varying rates of diseases, injuries, and health
states in human populations.
Fomite. Personal article—such as handkerchiefs, toothbrushes, drinking glasses—that, if shared, may carry agents
from host to host due to the relatively intimate contact with it.
General Fertility Rate (GFR). The ratio of live births to the number of women of childbearing age (usually assumed to be 15-44
years of age). The rate at which women in the population are having babies.
Gross Reproduction Rate (GRR). The ratio of female live births to the number of women of childbearing age (15-44).
Handicap. A disadvantage for any individual, resulting from a disability, that limits or prevents the fulfillment of a role
that would be considered normal for that individual (given the individual's age, sex, social status, and
Health. A state of complete physical, mental, and social well-being, and not the mere absence of disease or infirmity.
Health Maintenance. Measures targeted at disease-free individuals with the aim of preventing the occurrence of disease;
Health Promotion. Measures targeted at disease-free individuals with the aim of enhancing their level of wellness.
Health Restoration. Measures targeted at diseased individuals with the aim of restoring them to good health.
Host. The person (or other organism) in which the disease process takes place.
Impairment. Any loss or abnormality of psychological, physiological, or anatomical nature.
Incidence. The rate of new cases. The rate at which a disease spreads.
Infectivity. The ability of an agent to invade and reproduce itself in an exposed host.
Lifetime Prevalence. The proportion of persons within a population who have ever suffered from the disease or condition of
Morbidity. Statistics on cases of disease.
Mortality. Statistics on deaths.
Natality. Statistics on births.
Neonatal Period. The first 28 days of life.
Net Reproduction Rate (NRR). The ratio of female live births minus female infant mortality in relation to the number of women
of childbearing age (15-44). A more accurate approximation than gross reproduction rate of the rate at which women are giving
birth to their own replacements in the population.
Odds Ratio. An approximation of relative risk calculatable from case-control studies; also known as relative odds.
Pathogenicity. The ability of an agent to produce disease in an infected host.
Perinatal Period. The period around the birth of a child. Perinatal period I extends from 28 weeks after conception until
1 week after birth. Perinatal period II extends from 20 weeks after conception until 4 weeks after birth.
Period Prevalence. The rate of current cases during some defined period of time.
Point Prevalence. The rate of current cases on one particular day.
Postneonatal Period. The period after the first 28 days of life but before the infant is 1 year old.
Prevalence. The rate of current cases (whether new or not) in a population. Rate expressing the proportion of the population
at risk who suffered a given disease during a given time.
Primary Prevention. Keeping disease from occurring in the first place; aims to lower incidence by keeping new cases from
Rate. An expression of the proportion of some population who experienced a specified event.
Ratio. An expression of the relationship between two quantities.
Relative Odds. An approximation of relative risk calculatable from case-control studies; also known as odds ratio.
Relative Risk. The ratio of the risk of disease (incidence rate) among those exposed to some risk factor to the risk among
the unexposed; also known as risk ratio.
Restricted-Activity Days. Days on which one reduces the range of activities due to illness.
Secondary Prevention. Early detection and treatment of disease; aims to lower prevalence by reducing the average duration
Secular Trend. A pattern of continuing increase or decrease over a period of 10 years or more.
Significance. The degree to which one can be certain that two measures are truly different and not the result of random errors
in measurement. A significant difference is presumed to be a real difference; a nonsignificant difference is presumed to be
due to measurement or sampling error and thus no real difference exists.
Tertiary Prevention. The prevention of death or other long-term afterČeffects of illness.
Total Fertility Rate (TFR). The sum of annual age-specific birth rates for women aged 10-49. A more accurate estimate than
general fertility rate of the rate at which women are having babies.
Vector. Originally, a blood-sucking insect that carries a disease agent from host to host. Now, generally used for any
animal that thus carries disease and sometimes for nonliving vehicles of infection as well.
Vehicle. Any nonliving object or substance that carries an agent from host to host, such as fomites, water, or food.
Virulence. The ability of an agent to produce severe disease in a diseased host.
Vital Statistics. Records of the numbers of births, marriages, divorces, and deaths; sometimes used to mean all health-related