Microbes Can Infect and Make Us Sick

by National Institute of Health

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Microbes Can Make Us Sick

According to health care experts, infectious diseases caused by microbes are responsible for more deaths worldwide than any other single cause. They estimate the annual cost of medical care for treating infectious diseases in the United States alone is about $120 billion.

The science of microbiology explores how microbes work and how to control them. It seeks ways to use that knowledge to prevent and treat the diseases microbes cause. The 20th century saw an extraordinary increase in our knowledge about microbes. Microbiologists and other researchers had many successes in learning how microbes cause certain infectious diseases and how to combat those microbes.

Unfortunately, microbes are much better at adapting to new environments than are people. Having existed on Earth for billions of years, microbes are constantly challenging human newcomers with ingenious new survival tactics.

Many microbes are developing new properties to resist drug treatments that once effectively destroyed them. Drug resistance has become a serious problem worldwide. Changes in the environment have put certain human populations in contact with newly identified microbes that cause diseases we have never seen before, or that previously occurred only in isolated populations. Newly emerging diseases are a growing global health concern. Since 1976, scientists have identified approximately 30 new pathogens.

Microbes Can Infect Us

Below are some of the many different ways you can get infected by germs.

Some Microbes Can Travel Through the Air

You can transmit microbes to another person through the air by coughing or sneezing. These are common ways to get viruses that cause colds or flu, or the bacteria that cause tuberculosis (TB). Interestingly, international airplane travel can expose you to germs not common in your own country.

Close Contact Can Pass Germs to another Person

Scientists have identified more than 500 types of bacteria that live in our mouths. Some keep the oral environment healthy, while others cause problems like gum disease. One way you can transmit oral bacteria is by kissing.

Microbes such as HIV, herpes simplex virus, and gonorrhea bacteria are examples of germs that can be transmitted directly during sexual intercourse.

You Can Pick Up and Spread Germs by Touching Infectious Material

A common way for some microbes to enter the body, especially when caring for young children, is through unintentionally passing feces from hand to mouth or the mouths of young children. Infant diarrhea is often spread in this way. Day care workers, for example, can pass diarrhea-causing rotavirus or Giardia lamblia (protozoa) from one baby to the next between diaper changes and other childcare practices.

It also is possible to pick up cold viruses from shaking someone's hand or from touching contaminated surfaces, such as a handrail or telephone.

A Healthy Person Can Carry Germs and Pass Them onto Others

The story of "Typhoid Mary" is a famous example from medical history about how a person can pass germs on to others, yet not be affected by those germs. The germs in this case were Salmonella typhi bacteria, which cause typhoid fever and are usually spread through food or water.

In the early 20th century, Mary Mallon, an Irish immigrant, worked as a cook for several New York City families. More than half of the first family she worked for came down with typhoid fever. Through a clever deduction, a researcher determined that the disease was caused by the family cook. He concluded that although Mary had no symptoms of the disease, she probably had had a mild typhoid infection sometime in the past. Though not sick, she still carried the Salmonella bacteria and was able to spread them to others through the food she prepared.

Germs from Your Household Pet Can Make You Sick

You can catch a variety of germs from animals, especially household pets. The rabies virus, which can infect cats and dogs, is one of the most serious and deadly of these microbes. Fortunately, rabies vaccine prevents animals from getting rabies. Vaccines protect people from accidentally getting the virus from an animal. They also prevent people who already have been exposed to the virus, such as through an animal bite, from getting sick.

Dog and cat saliva can contain any of more than 100 different germs that can make you sick. Pasteurella bacteria, the most common, can be transmitted through bites that break the skin causing serious, and sometimes fatal, diseases such as blood infections and meningitis. Meningitis is the inflammation of the lining of the brain and spinal cord.

Warm-blooded animals are not the only ones that can cause you harm. Pet reptiles such as turtles, snakes, and iguanas can give Salmonella bacteria to their unsuspecting owners.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.