Influenza Research

By the late 1890s and early 1900s, scientists understood that microorganisms caused disease. Most disease research focused on bacteria, which are large enough to be visible under a light microscope and can be isolated using filters. But technology at the time prevented scientists from identifying a disease-causing agent as small as a virus.

In the 1890s German bacteriologist Richard F. J. Pfeiffer reported that he had identified the bacterium Haemophilus influenzae as the cause of influenza. Further investigation indicated, however, that this bacterium was not always present in people with influenza. Scientists concluded that the Haemophilus influenzae bacterium probably played a role in secondary infections.

Meanwhile, the long-held belief that influenza only occurred in humans was overturned. Around 1930 American bacteriologist Richard E. Shope showed that it was possible to transfer an influenza-like disease from one pig to another. Thereafter scientists chiefly used animals in their research on influenza.

In 1933 English physicians Wilson Smith, Christopher H. Andrewes, and Patrick P. Laidlaw removed secretions from the throat of a human flu victim, filtered out a suspect infectious agent, and injected the material into ferrets. The ferrets then developed influenza, thereby demonstrating that the infectious agent caused influenza. Research performed by other researchers eventually proved that the infectious agent was the influenza A virus. The influenza B virus was isolated in 1940, and the influenza C virus in 1950.

In 1941 scientists demonstrated that a vaccine could control influenza. The first vaccine was developed to protect soldiers during World War II (1939-1945). Early influenza vaccines produced from the 1940s to the mid-1960s were all made from killed viruses, which cannot cause infection. But these early vaccines contained impurities that produced fever, headaches, and other severe side effects. Improved pharmaceutical procedures have made today’s vaccines almost free from impurities, greatly reducing the chance that the vaccines will cause side effects.

Despite these improvements, developing influenza vaccines remains a challenge. Current vaccines do not provide 100 percent protection against influenza, and they can be quickly rendered ineffective by changes in the viruses themselves. Some scientists, believing that vaccines will never be able to completely control influenza, work to expand the number and variety of drugs available to treat the disease once symptoms appear. Until a cure for influenza is discovered, public health officials hope that identifying and reporting new viral strains quickly will result in timely actions that prevent the recurrence of deadly pandemics. Even in best-case scenarios, however, influenza is expected to remain a formidable opponent of human health.

Entrepreneur

Entrepreneur, one who assumes the responsibility and the risk for a business operation with the expectation of making a profit. The entrepreneur generally decides on the product, acquires the facilities, and brings together the labor force, capital, and production materials. If the business succeeds, the entrepreneur reaps the reward of profits; if it fails, he or she takes the loss.

The Austrian-American economist Joseph A. Schumpeter stressed the role of the entrepreneur as an innovator, the person who develops a new product, a new market, or a new means of production. One important example was Henry Ford. In the industrialized economies of the late 20th century, giant corporations and conglomerates have largely replaced the individual owner-operator. There is still a place for the entrepreneur, however, in small businesses as well as in the developing economies of the Third World nations.

NEW DIRECTIONS IN WEIGHT CONTROL

The weight-loss goal of most obese dieters is to achieve an ideal weight often defined by celebrities and models in fashion magazines. But research over the last decade indicates that a 5- to 10-percent reduction in body weight is sufficient to significantly improve medical conditions associated with obesity, such as hypertension, diabetes mellitus, and elevated cholesterol levels. These health improvements occur even though patients may still be overweight.
These new weight-loss goals may be difficult for obese people to accept. Obese people often seek weight-loss goals that may be biologically impossible to achieve or, if achieved, cannot be maintained. One study of overweight women found that the average weight goal was a 30 percent reduction in body weight. Yet no obesity treatment produces long-term, maintainable weight losses significant enough for patients to reach this goal. Physicians and commercial weight-loss programs need to help obese people feel successful when more modest reductions in weight and significant improvements in health are achieved, many health experts believe.

OBESITY

OBESITY, medical condition characterized by storage of excess body fat. The human body naturally stores fat tissue under the skin and around organs and joints. Fat is critical for good health because it is a source of energy when the body lacks the energy necessary to sustain life processes, and it provides insulation and protection for internal organs. But the accumulation of too much fat in the body is associated with a variety of health problems. Studies show that individuals who are overweight or obese run a greater risk of developing diabetes mellitus, hypertension, coronary heart disease, stroke, arthritis, and some forms of cancer.

MEASURING OBESITY

The body mass index (BMI) is commonly used to determine desirable body weights. BMI is a measure of an adult’s weight in relation to height, and it is calculated metrically as weight divided by height squared (kg/m2). People with a BMI of 25.0 to 29.9 are considered overweight and people with a BMI of 30 or above are considered obese .

Body mass index only provides a rough estimate of desirable weight, however. Physicians recognize that many other factors besides height affect weight. Weight alone may not be an indicator of fat, as in the case of a bodybuilder who may have a high BMI because of a high percentage of muscle tissue, which weighs more than fat. Likewise, a person with a sedentary lifestyle may be within a desirable weight range but have excess fat tissue. In general, however, the higher the BMI, the greater the risk for developing serious medical conditions.

CAUSES OF OBESITY

A calorie is the unit used to measure the energy value of food and the energy used by the body to maintain normal functions. When the calories from food intake equal the calories of energy the body uses, weight remains constant. But when a person consumes more calories than the body needs, the body stores those additional calories as fat, causing subsequent weight gain. Consuming about 3,500 calories more than what the body needs results in a weight gain of 0.45 kg (1 lb) of fat.

TREATMENTS FOR OBESITY

Obesity can become a chronic lifelong condition caused by overeating, physical inactivity, and even genetic makeup. No matter what the cause, however, obesity can be prevented or managed with a combination of diet, exercise, behavior modification, and in severe cases, weight-loss medications and surgery.

Diets

The most common and conservative treatment for obesity utilizes a nutritionally balanced, low calorie diet. Most health-care professionals and commercial weight-loss programs recommend diets consisting of 1,200 to 1,500 calories per day, usually in the following proportions: 60 percent carbohydrate, 30 percent fat, and 10 percent protein. Research from university obesity treatment centers indicates that patients who follow a low calorie diet lose 10 percent of their initial weight in 20 weeks. Without further treatment, however, patients usually regain one-third of the weight in the following year.

A more aggressive approach for persons who are more than 20 kg (40 lb) overweight includes very low calorie diets ranging from 400 to 800 calories per day. These diets are usually based on four to five servings of a liquid formula each day. Candidates must be carefully screened and medically supervised while on the diet. People on very low calorie diets lose approximately 15 to 20 percent of their initial body weight in 16 weeks. Once they go off a very low calorie diet, they typically regain approximately one-half of that weight within a year.

Meal replacements are liquid shakes or portion-controlled meals that are substituted for one or two meals a day. They are typically used as part of a 1,200 to 1,500 calorie diet. Studies have shown that meal replacements are often more effective than very low calories diets, resulting in an increase in the amount of initial weight loss and enabling dieters to maintain their weight loss. Unlike very low calorie diets, meal replacements do not require that candidates receive extensive medical monitoring.

Exercise

Caloric restriction alone will not produce long-term weight loss. While the data from studies on the effect of exercise for short-term weight loss are contradictory, research clearly indicates that regular exercise is the single best predictor for achieving long-term weight control. Regular exercise will also improve some of the medical conditions associated with obesity, including elevated blood cholesterol, hypertension, and diabetes mellitus.

Behavior Modification

Many eating and exercise habits combine to promote weight gain. Certain times, places, activities, and emotions may be linked to periods of overeating or inactivity. Many obesity treatment programs recommend individuals keep a food diary that records all food or drink consumed, when and with whom it was consumed, and the mood or precipitating events that trigger eating. After one to two weeks, the diary may reveal a pattern of activities or negative emotions that lead to overeating. Once these eating cues are identified, techniques can be developed and practiced to prevent unwanted eating habits.

Weight-Loss Medications

Weight-loss medications of any type are only appropriate for people with a BMI of 30 or above, or a BMI of 27 or above accompanied by weight-related medical conditions such as diabetes mellitus or hypertension. Amphetamine drugs were formerly prescribed to combat obesity, but their well-documented side effects, including insomnia, anxiety, and tolerance (the need to take higher and higher doses to continue to produce the same effect), made them less popular by the late 1970s.

A renewed scientific and commercial interest in weight-loss medications was prompted by the approval by the Food and Drug Administration (FDA) of the appetite suppressant dexfenfluramine (sold under the brand name Redux) in 1996. Dexfenfluramine was the first weight-loss medication approved in the United States in over 20 years and the first ever approved for maintaining weight loss. Although never approved for long-term use by the FDA, a combination of two drugs, phentermine and fenfluramine, or phentermine and dexflenfluramine, popularly known as fen-phen, was used by millions of Americans to promote weight loss. Fenfluramine and dexfenfluramine were eventually associated with valvular heart disease, and the manufacturer withdrew these medications from the marketplace in 1997.

The FDA has approved two medications, sibutramine and orlistat, for long-term use in the treatment of obesity. Sibutramine (sold under the brand name Meridia) increases fullness, making the required dietary changes for weight loss and the maintenance of weight loss easier to accomplish. Unlike dexfenfluramine and fenfluramine, sibutramine does not appear to be associated with valvular heart disease, although a small number of patients may develop significant increases in blood pressure. Orlistat (sold under the brand name Xenical) works by blocking the absorption of fat. Scientists are also investigating the hormone leptin, which plays a role in obesity in mice, as a possible treatment for obesity in humans.

Over a six-month period, weight-loss medications may result in a 10-percent body weight reduction. Weight loss slows or stops after six months, and discontinuing medication usually causes weight regain. The continued use of medications keeps most of the lost weight from returning for two years. Many experts recommend that medications for weight control be used continuously, like medications for diabetes mellitus and hypertension. Unfortunately, few studies have examined the consequences of long-term use of weight-control medications.