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People often think of health and illness in terms of a single person contracting an infection such as the flu by being exposed to the virus * , or a person trying to avoid an infection by careful hand washing or getting a shot. However, there are other, broader ways to look at health and illness that go beyond just one individual person. The field of public health looks at a larger view that includes whole populations and health practices. Public health involves the field of medicine devoted to disease prevention and control, environmental health, and health promotion and educational activities to improve general health and safety.
In the field of public health, the science of epidemiology (eh-pih-dee-me-AH-luh-jee) is an important tool in understanding human diseases. Epidemiology is the study of what causes disease, how it spreads, and all the factors that influence it. Epidemiologists (eh-pih-dee-me-AH-lo-jists), the scientists involved in public health, study epidemics * , or outbreaks, to determine the source of the infection and to prevent its further spread.
Public health officials look at patterns of infections and other diseases to see if changes occur over time. The goal of this monitoring (called surveillance) is to recognize an outbreak early so that something can be done about it. Once an outbreak has been identified, epidemiologists look for the source of infection. Infections are spread through one of four routes:
- direct contact with someone who is infected
- a common source, such as contaminated water
- the air, such as through a contaminated ventilation system
- a vector * , such as a mosquito or a tick that spreads an infection through its bite
In addition, certain factors may increase the risk of becoming sick. Poverty, poor sanitation, crowded living conditions, and malnutrition all contribute to the spread of infections. Climate can also play a role. For example, the hot and humid environments found in the tropics and subtropics can contribute to particularly rapid growth of certain microorganisms * and vectors. Infections happen in every climate and part of the world, however.
* virus (VY-rus) is a tiny infectious agent that can cause infectious diseases. A virus can only reproduce within the cells it infects.
* epidemics (eh-pih-DEH-miks) are outbreaks of diseases, especially infectious diseases, in which the number of cases suddenly becomes far greater than usual. Usually epidemics are outbreaks of diseases in specific regions, whereas widespread epidemics are called pandemics.
* vector (VEK-tor) Is an animal or insect that carries a disease and transfers it from one host to another.
* microorganisms are tiny organisms that can be seen only using a microscope. Types of microorganisms include fungi, bacteria, and viruses.
Local public health departments coordinate surveillance efforts and are responsible for creating plans to prevent and control outbreaks and for informing and educating the public. The U.S. Centers for Disease Control and Prevention (CDC) is one of the main federal agencies responsible for protecting the health and safety of people in the United States and abroad. The CDC provides health information, guidelines for disease prevention and safety, public health policy, and research. The surgeon general, who is part of the U.S. department of health and who is appointed by the president, is the nation's leading spokesperson on public health issues.
Public Health Tools
Public health programs employ a number of tools to prevent disease, to change behaviors that contribute to the spread of disease, and to monitor and control the spread of infections.
Most people do not like the idea of getting shots. However, widespread immunization programs have saved millions of lives and have proven to be an incredible public health success story. Take the example of polio (paralytic poliomyelitis, po-lee-o-my-uh-LYE-tis). Polio, a viral infection that causes paralysis * in approximately 1 in 200 people infected, reached a peak in the United States in 1952 with over 20,000 cases of paralytic polio reported. Following the introduction of polio vaccines * in 1955 and 1961, there were only 61 cases in 1965. The last cases of naturally occurring (wild) polio in the United States were reported in 1979. The World Health Organization (WHO) hopes to eradicate polio throughout the world by providing vaccination in areas where polio still occurs, primarily in India and parts of Africa and the eastern Mediterranean.
Immunization programs also have been successful in preventing smallpox, a disfiguring, often fatal infection caused by the variola (vere-O-luh) virus. Following a worldwide immunization program, in 1980 WHO declared that smallpox had been eradicated. In developed countries, vaccinations have reduced the number of cases and the severity of many childhood diseases that were once common and feared, including measles * , mumps * , and diphtheria * .
Conditions in developing countries are very different, however. Many diseases that are preventable with routine vaccination continue to occur in large epidemics in many areas because these countries lack the money required for immunizations. Worldwide immunization rates have been declining in recent years. By 2000, 37 million children throughout the world were not immunized during their first year of life. Giving these children vaccines that are part of normal health care in the developed world could save 5,000 children's lives every day.
* paralysis (pah-RAH-luh-sis) is the loss or impairment of the ability to move some part of the body.
* vaccine (vok-SEEN) is a preparation of killed or weakened germs, or a part of a germ or product it produces, given to prevent or lessen the severity of the disease that can result if a person is exposed to the germ itself. Use of vaccines for this purpose is called immunization.
* measles (ME-zuls) is a viral respiratory infection that is best known for the rash of large, flat, red blotches that appear on the arms, face, neck, and body.
* mumps is a contagious viral infection that causes inflammation and swelling in the glands of the mouth that produce saliva.
After 10 years, these careful measures paid off: the last natural case of smallpox was reported in Somalia in 1977. One fatal case of smallpox occurred in the United Kingdom in 1978 following a laboratory accident. In 1980, after careful confirmation, WHO certified that smallpox had been completely erased.
Controlling the spread of disease
Efforts to control the spread of infectious diseases include insect control programs and improved sanitation. For example, malaria (mah-LAIR-e-uh), a tropical disease carried by mosquitoes, once was found along the coast of the southeastern United States but was wiped out following insect control programs during the 1940s. Worldwide, however, cases of malaria and malaria deaths are on the rise because of difficulty in eliminating mosquito breeding places and the lack of medical resources to treat the disease.
To prevent the spread of disease through contaminated water, widespread sanitation practices also are monitored, including sewage disposal, water treatment plants, and solid waste (such as trash) disposal. In addition, safety standards for processing, packaging, and selling food protect people from contaminated foods.
The effectiveness of well-organized public health efforts is easy to see in a country such as the United States where public health programs can be carried out. It is a sad fact, however, that about one sixth of the world's population does not have access to clean drinking water. WHO also estimates that one third of the world's population does not have access to essential medications. Unfortunately, the lack of resources has hindered progress in developing countries where public health initiatives would have the most benefits.
* diphtheria (dif-THEER-e-uh) is an infection of the lining of the upper respiratory tract (the nose and throat). It is a serious disease that can cause breathing difficulty and other complications, including death.
Other public health campaigns
In addition to working to control the spread of infectious diseases, public health programs are aimed at preventing injuries, reducing the risk of environmental hazards, promoting healthy lifestyles, and making health care available to as many people as possible. Mandatory seatbelt and bike helmet laws are the result of public health campaigns. Public health efforts to reduce lead in the environment by banning lead-based paint and leaded gasoline have decreased the number of children ages 1 to 5 who have elevated levels of lead in their blood by more than 90 percent since the late 1970s. Education through advertisements and public information programs, such as car seat safety, hand-washing, safer-sex, and stop-smoking campaigns, is another way to change behavior and prevent diseases.
Public health agencies also promote healthy living in local communities by providing access to health care. Examples include setting up school health programs and providing medical insurance programs for the uninsured. The National Health Service Corps and the Indian Health Service provide medical care where it would not otherwise be available.
SARS: A New Virus
Severe acute respiratory syndrome (SARS) first appeared in November 2002 and soon caused fear as the number of cases climbed into the thousands. What was causing this flulike illness? How serious was the threat?
It took years to identify the virus behind another frightening illness—AIDS. But thanks to advances in medical science and epidemiology, scientists identified a coronavirus as the probable culprit behind SARS within a matter of weeks.
Symptoms of SARS include fever, cough, headache, body aches, and chills. In some cases, SARS can cause breathing difficulty and, rarely, death. The vast majority of people survive, and with the rapid response of public health officials and quarantine methods, SARS can be contained.
This new virus is not alone. Public health officials believe that the way we live—and travel around the world—may play a significant role in the spread of many new diseases. For example, feeding animal remains to livestock helped spur Creutzfeldt-Jakob disease (CJD).
As some diseases are wiped out, like polio, others will continue to emerge. With medical advances, however, we are well equipped at identifying their causes and ways that they can be treated and prevented.
Stamping out Smallpox
Smallpox was eliminated through a global immunization campaign conducted by the World Health Organization (WHO). Believed to have originated in Egypt or India, the 3,000-year-old disease regularly rampaged across continents, causing devastating epidemics that often cut into populations and changed history. No effective treatment was ever found for the disease, which, in addition to causing blindness, killed close to a third of its victims.
In the early 1950s, about 50 million cases of smallpox were tracked around the globe each year. By 1967 that number had dropped to 10 to 15 million cases due to vaccination, and that year WHO began a plan to rid the world of smallpox. The organization used surveillance techniques to monitor outbreaks of the disease. When the typical rash was observed, often on the face and hands, workers quarantined (or isolated) the patient and then tracked down everyone who had been in close contact with the person so that they could be vaccinated.
* chronic (KRAH-nik) means continuing for a long period of time.
* biological warfare is a method of waging war by using harmful microorganisms to purposely spread disease to many people.
Public Health in the Twenty-First Century
With the increased success of infection control measures, routine vaccination, and advances in the treatment of infectious diseases, there has been a shift in the focus of public health toward chronic * diseases, injury prevention, and environmental safety. However, with the appearance of new infections, emerging resistance to some medications, and the concern about biological warfare * , combating infectious diseases will continue to be an important challenge within the field of public health.
Top Public Health
Achievements, 1900 to 1999
During the 1900s, Americans added on average 30 years to their life span, with 25 years of this gain coming from advances in public health programs, according to the U.S. Centers for Disease Control and Prevention. The most notable public health achievements in the 1900s include:
- increased motor vehicle safety
- safer workplaces
- greater control of infectious diseases
- fewer deaths from heart disease and stroke *
- safer and healthier foods
- healthier mothers and babies
- widespread fluoridation * of drinking water
- recognition of tobacco as a health hazard
* stroke is a brain-damaging event usually caused by interference with blood flow to the brain. A stroke may occur when a blood vessel supplying the brain becomes clogged or bursts, depriving brain tissue of oxygen. As a result, nerve cells in the affected area of the brain, and the specific body parts they control, do not properly function.
* fluoridation is the process of adding fluoride to drinking water to help prevent tooth decay.
National Institute of Allergy and Infectious Diseases (NIAID), Building
31, Room 7A-50, 31 Center Drive MSC 2520, Bethesda, MD 20892. The NIAID,
part of the National Institutes of Health, posts information about
infectious diseases and public health at its website.
U.S. National Library of Medicine, 8600 Rockville Pike, Bethesda, MD
20894. The National Library of Medicine has a website packed with
information on infectious diseases and public health, consumer
resources, dictionaries and encyclopedias of medical terms, and
directories of doctors and helpful organizations.
U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton
Road, Atlanta, GA 30333. The CDC offers information on
infectious diseases and public health efforts to control them on its
World Health Organization (WHO), Avenue Appia 20, 1211 Geneva 27,
Switzerland. WHO tracks disease outbreaks around the world and offers
information about infectious diseases and public health programs around
the world at its website.
The Johns Hopkins infectious diseases website provides information about
numerous infectious diseases and other public health issues.