New and re-emerging U.S. Killers
Most Americans are aware of the epidemic of acquired immunodeficiency syndrome (AIDS) caused by the human immunodeficiency virus (HIV) and the increase in tuberculosis (TB) cases earlier this decade in the United States. In fact, there has been a general resurgence of infectious diseases throughout the world, including significant outbreaks of cholera, malaria, yellow fever and diphtheria.
In the U.S., new diseases also have appeared, including Lyme disease, Legionnaires' disease and most recently, Hantavirus pulmonary syndrome (HPS). HPS was first recognized in the southwestern United States in 1993 and has since been detected in more than 20 states and in several other countries in the Americas. Other new or re-emerging domestic threats include multidrug-resistant TB; antibiotic-resistant bacteria that cause ear infections; fungal infections; and diarrheal disease cause by the parasite Cryptosporidium parvum and by certain toxigenic strains of Escherichia coli bacteria.
How have some disease re-emerged decades, and even centuries, later in new locales? Where will the next outbreaks be?
The major killers worldwide
Infectious diseases are the leading cause of death worldwide. Surprisingly, the leading killers among infectious microbes today are not the frightening newcomers that make headlines. They're such age-old scourges as tuberculosis and measles. All but vanquished in highly developed areas such as Europe, North America, Australia and Japan, these two diseases take millions of lives each year, particularly in developing nations.
Each year TB kills 3 million and infects 8 million more. Another deadly infection is measles, now rare in industrialized nations due to widespread vaccinations. One of the most contagious of all human infections, measles takes more than 1 million lives worldwide every year.
What has aggravated the revival of some diseases once thought to be under control? What makes some populations more susceptible than others?
Microbes that threaten us
In their own struggle to survive, some microbes attack humans. How do they invade? How do they make us sick? How do we fight back?
Invading the body takes strategy and luck. Microbes can enter the body through eyes, nose, ears, mouth, cuts, burns, and punctures. For successful entry, however, microbial invaders first must break through the body's natural lines of defense such as skin, mucus, and stomach acids and enzymes. Once inside the body, a microbe attaches itself to a cell surface or actually invades the cell.
The body fights back with killer white blood cells and antibodies. If a bacterial infection persists, antibiotics offer a second line of defense.
Some drugs kill bacteria outright; some cripple bacteria enough for the body's immune system to destroy the remains. Vaccines prevent infection by making the body resistant to particular invaders. But the battle against microbe invaders is never-ending as microbes constantly mutate to avoid being destroyed by antibodies and antibiotics.
"Germs" we can't live without
Life on earth would not exist without microbes. They are everywhere--in the air, in our food, in our water. While many microbes are harmful, most are harmless or even helpful.
Some microbes return nutrients such as nitrogen to the soil, helping farmers grow crop plants. Some microbes digest oil and pesticides, helping clean up the environment. Water treatment plants add microbes to help purify the water.
Many microbes do good deeds for food. Inside the stomach and intestines, billions of microbes break down food into nutrients the body needs and make digestive gas in the process. Bacteria turn milk into yogurt and cheese. When yeasts (fungi) digest the sugars in grains or grapes, they convert the sugars into alcohol for making beer and wine. When yeasts digest sugars in bread dough, they give off carbon dioxide gas to make the bread rise.
Microbes are even food for other microbes and tiny animals, so they are an essential part of any food web.
The impact these smallest of germs have on our lives is far-reaching, affecting our diets, our environment and our health.
Winning the war against infection: What you can do
Out of sight, out of mind ... that is what most people think about microbes. But think again. Microbes are everywhere--on your skin, in your bed, and under your feet. While most mind their own business, others invade our bodies in their struggle to survive. In addition to the body's natural defenses, individuals can fight back against infection with their own arsenal of guerilla tactics.
Careful hand washing with soap after using the bathroom and before eating is a practical way to prevent the spread of microbes. Avoiding spoiled or undercooked foods is another way. Keeping cutting boards clean by washing with soap and drying after each use prevents the boards from becoming bacterial breeding grounds.
Using soap to wash dishes keeps them squeaky clean and microbe free. Better yet, wash them in the dishwasher. Many microbes can't stand the heat. And don't forget dishcloths and sponges. A little bleach can rid them of bacteria, too.
Staying current with vaccinations primes the body's immune system to kill microbial invaders. If bacteria do make you sick, antibiotics can help. One of the best ways to battle infection is to finish a prescribed medication. Completing the course of a prescription not only helps destroy all harmful bacteria but also prevents mutation and multiplication of survivors.
What are other practical ways to prevent infections from spreading--at home, at school, at work?
Drug Research
Scientific advances within the last 50 years have helped control many infectious diseases: pneumonia, strep infections, syphilis, meningitis, diphtheria, whooping cough, polio, and measles. Researchers today are on the verge of greater medical discoveries than ever before.
Since 1995 researchers have made breakthrough discoveries in identifying the genetic blueprints of bacteria. Deciphering the organisms' genetic make-up may reveal what makes some strains virulent and others harmless, leading to new and improved antibiotic drugs.
Discoveries in anti-infective medicine are the result of work by scientists in government, academia and industry. Domestic research by U.S. research-based pharmaceutical companies is estimated to grow to $15 billion in 1997, an increase of 12.5% over 1996. In fact, U.S. companies account for more than one third of the pharmaceutical research and development conducted worldwide. In fiscal year 1997, the National Institute of Allergy and Infectious Diseases (NIAID) contributed 84% of its total budget to support scientific research at institutions across the country and worldwide.
What is the average cost to develop a new drug? How long does it take to get a new medicine from the laboratory to your local pharmacy?
Medical Breakthroughs in the 20th Century
In the early 1900s, medical options against infections were very limited. In many cases physicians confronted with a potentially fatal illness could do nothing. Close to a million children died each year from bacteria-caused infections, which were more likely to be life threatening than they are today.
Since the start of the century, unprecedented advancements have been made in the prevention and treatment of fatal and infectious diseases.
The discovery of penicillin by Alexander Fleming in 1928 provided the starting point for one of the most significant advances ever. Mass production of the "miracle drug" in 1943 and its public availability in 1945 created a worldwide sensation. Children bounced back from ailments that months before had been considered serious, even deadly. Other dreaded diseases became trivial with the quick discovery of streptomycin and other antibiotic products.
Polio vaccination was another milestone. From 1916 to 1955, parents feared the disease that paralyzed or killed up to 40,000 children each year. In 1955, Dr. Jonas Salk introduced the first polio vaccine. Millions received the Salk series of injections. Then in 1961, Dr. Albert Sabin developed a less expensive oral vaccine. After the start of Salk's mass vaccination campaign, the incidence of polio in Western Europe and North America dropped from 76,000 in 1955 to less than 1000 in 1967.
Today hundreds of synthetic drugs fight diseases once thought incurable. The first synthesized antibiotic, tetracycline, was developed in 1965 by a U.S. pharmaceutical firm. Copying chemical formulas of natural antibiotics produced the first synthetic drugs. Now chemists create synthetic drugs that bring new hope in battling microbes that have grown resistant to traditional antibiotics.
A new class of anti-HIV compounds, protease inhibitors, has been developed. Protease ("pro-tee-ace") inhibitors can reduce the number of new, infectious copies of HIV made inside cells, thus slowing the spread of HIV inside the body. Several pharmaceutical companies have marketed protease inhibitors and are investigating their use in acute infection, pediatric disease and combination regimens.
What are the next great frontiers in medical research? What are the implications for consumers? What advances can we expect in the near future?
|
Rate this article to help us improve.
