Microorganisms

They are invisible to us, but each day we are exposed to multitudes of very tiny microorganisms. Microorganisms live everywhere - in air, soil, rock and water. For the most part, they do us no harm, but sometimes we encounter disease-causing (pathogenic) microorganisms that make us sick. These can be spread to humans from:

• other humans from sneezing or coughing
• animals by droppings or saliva (Read about "Animal & Insect Borne Diseases")
• insect bites (Read about "Insect Bites")
• contaminated food or water (Read about "Food Safety")

Once microorganisms invade our bodies, they can settle in. They can gobble up nutrients and energy, and can produce toxins, which are like poisons. Those toxins can cause symptoms of common infections, like fevers, sniffles, rashes, coughing, vomiting and diarrhea. (Read about "Diarrhea") There are four major groups of microorganisms: bacteria, viruses, fungi and protozoa (a type of parasite). Disease microorganisms (most people call them germs) can be from any of these four categories.

Bacteria

Bacteria are microscopic living things that have only one cell (unicellular) and are one of three shapes, rods, balls or spirals. Some bacteria cells exist as individuals while others cluster together to form pairs, chains, squares or other groupings. Vast numbers of bacteria live in, and on, our bodies. Some are beneficial. For example, some bacteria help us digest food, destroy disease-causing cells and give the body needed vitamins. (Read about "Vitamins & Minerals") However, some types of infectious bacteria can make you ill. Some examples of diseases caused by bacteria are:

• anthrax (Read about "Biological Health Threats")
• bacterial vaginosis (Read about "Bacterial Vaginosis")
• botulism (Read about "Biological Health Threats")
• campylobacteriosis (Read about "Campylobacter")
• E. coli (Read about "E. coli")
• group B strep (Read about "Group B Strep")
• impetigo (Read about "Impetigo")
• Legionnaires' disease (Read about "Legionnaires' Disease & Pontiac Fever")
• listeria (Read about "Listeriosis")
• Lyme disease (Read about "Lyme Disease")
• meningitis (Read about "Encephalitis & Meningitis")
• otitis externa (Read about "Otitis Externa")
• pelvic inflammatory disease (PID) (Read about "Pelvic Inflammatory Disease")
• peptic ulcers (Read about "Peptic Ulcers")
• pneumonia (Read about "Pneumonia")
• pneumonic plague (Read about "Biological Health Threats")
• rheumatic fever (Read about "Rheumatic Fever")
• salmonella (Read about "Salmonella")
• shigellosis (Read about "Shigellosis")
• staph infection (Read about "Staph & MRSA")
• STDs such as chlamydia, gonorrhea, syphilis (Read about "STD's")
• strep throat (Read about "Sore Throat (Pharyngitis) & Strep Throat")
• swimmer's ear (Read about "Otitis Externa")
• tetanus (Read about "Wound Care")
• tuberculosis (Read about "Tuberculosis")
• urinary tract infections (Read about "Urinary Tract Infections")
• Whipple's disease (Read about "Whipple's Disease")

There are other bacteria that can infect people, according to the Centers for Disease Control and Prevention (CDC), they include:

• Clostridium difficile - C. difficile is a bacterium that causes diarrhea and more serious intestinal conditions such as colitis, sepsis, and rarely, death. (Read about "Clostridium Difficile" "Ulcerative Colitis" "Sepsis") Symptoms include:
  • watery diarrhea (at least three bowel movements per day for two or more days)
  • fever
  • loss of appetite
  • nausea
  • abdominal pain/tenderness

  C. difficile is generally treated for 10 days with antibiotics (Read about "Antibiotics") prescribed by your healthcare provider, according to CDC. People in good health usually don't get C. difficile disease. People who have other illnesses or conditions requiring prolonged use of antibiotics and the elderly are at greater risk of acquiring this disease. The bacteria are found in the feces. People can become infected if they touch items or surfaces that are contaminated with feces and then touch their mouth or mucous membranes. Healthcare workers can spread the bacteria to other patients or contaminate surfaces through hand contact.

• Brucella - Brucellosis is an infectious disease caused by the bacteria of the genus Brucella. These bacteria are primarily passed among animals, according to CDC. Various Brucella species affect sheep, goats, cattle, deer, elk, pigs, dogs and several other animals. Humans become infected by coming in contact with animals or animal products that are contaminated with these bacteria.

  In humans, brucellosis can cause a range of symptoms that are similar to the flu and may include fever, sweats (Read about "Sweating"), headaches, back pains and physical weakness. Severe infections of the central nervous systems or lining of the heart may occur. Brucellosis can also cause long-lasting or chronic symptoms that include recurrent fevers, joint pain and fatigue.

  Brucellosis is not very common in the United States, where100 to 200 cases occur each year. But brucellosis can be very common in countries where animal disease control programs have not reduced the amount of disease among animals.

  CDC says you should not consume unpasteurized milk, cheese, or ice cream while traveling. If you are not sure that the dairy product is pasteurized, don't eat it. There is no vaccine available for humans.

• Yersinia - Yersiniosis is an infectious disease caused by a bacterium of the genus Yersinia. Most people are infected by Yersinia enterocolitica. The enterocolitica bacterium is related to Y. pestis, which causes plague. The major reservoir for this bacterium is pigs. Most people are infected by eating undercooked pork products, according to CDC. Drinking contaminated unpasteurized milk or untreated water can also transmit the infection.

  Infection most often happens to children. Usually children will develop a fever, abdominal pain and diarrhea (Read about "Diarrhea"), which is often bloody. Symptoms can last 1 to 3 weeks or longer. In older children and adults, right-sided abdominal pain and fever may be the main symptoms, and may be confused with appendicitis. (Read about "Appendicitis")

  CDC says the infection is rare about one person in 100,000 people is infected each year. It is more common in the winter and more common in children than adults.

• Vibrio - The Vibrio vulnificus bacterium is part of the same group of bacteria that causes cholera. The bacterium requires warm salt water to survive. Most cases of infection in the United States occur along the coast of the Gulf of Mexico.

  V. vulnificus can infect people in one of two ways. Open wounds that are exposed to salt water that contains V. vulnificus can result in skin breakdown and ulceration. V. vulnificus can invade the blood stream of people who have compromised immune systems ((Read about "The Immune System"), with potential deadly effects. The second means of infection is when people ingest the bacterium, usually by eating contaminated raw shellfish. This can result in vomiting, diarrhea and abdominal pain. Again, people with compromised immune systems face more complications.

  CDC says that Vibrio infection is under-reported but there are at least 900 cases reported each year.

Viruses

Viruses are the most primitive of microorganisms and are much smaller than bacteria. A virus is basically a tiny bundle of genetic material carried in a shell called the viral coat or envelope. Viruses only exist to reproduce. To do that, they have to take over suitable host cells. They invade the cells and once inside, multiply, killing the host cells in the process. This is what makes you sick. Viruses are easily destroyed by disinfectants outside the body, but can be difficult to eliminate once infection has taken place. The following are examples of viral infections:

• AIDS (Read about "HIV / AIDS")
• avian influenza (Read about "Bird Flu")
• chicken pox (Read about "Childhood Illnesses")
• common cold (Read about "The Common Cold")
• coronaviruses (Read about "Coronaviruses")
• Dengue fever (Read about "Dengue Fever")
• Ebola (Read about "Ebola")
• enteroviruses (Read about "Enteroviruses")
• fifth disease (Read about "Fifth Disease")
• flu (Read about "Influenza")
• hand, foot and mouth disease (Read about "Hand, Foot and Mouth Disease")
• hepatitis viruses (Read about "Hepatitis A" "Hepatitis B" "Hepatitis C" "Hepatitis D" "Hepatitis E")
• herpes (Read about "STD's" "Herpes")
• human papillomavirus (Read about "STD's")
• measles (Read about "Childhood Illnesses")
• molluscum contagiosum (Read about "Molluscum Contagiosum")
• mononucleosis (Read about "Mononucleosis")
• mumps (Read about "Childhood Illnesses")
• noroviruses (Read about "Noroviruses")
• rabies (Read about "Rabies")
• respiratory syncytial virus (Read about "Respiratory Syncytial Virus"
• Rocky Mountain spotted fever (Read about "Rocky Mountain Spotted Fever")
• roseola (Read about "Roseola")
• rotavirus (Read about "Rotavirus")
• rubella (Read about "Childhood Illnesses")
• severe acute respiratory syndrome (Read about "SARS")
• shingles (Read about "Shingles")
• smallpox (Read about "Biological Health Threats")
• viral meningitis (Read about "Encephalitis & Meningitis")
• viral pneumonia (Read about "Pneumonia")
• viral croup (Read about "Croup")
• warts (Read about "Warts")
• West Nile virus (Read about "West Nile Virus")

Some other viruses that can make people sick, according to the Food and Drug Administration (FDA) include:

• Hantaviruses - are a group of viruses that are carried by rodents. One of them is found in deer mice in North America. That virus is the cause of Hantavirus Pulmonary Syndrome (HPS) in people. Humans can contract the disease when they come into contact with infected rodents or their urine and droppings. HPS was first recognized in 1993 and has since been identified throughout the United States. Although relatively rare, HPS is potentially deadly.

  Early symptoms include chills, fever, and muscle aches. Left unchecked, the disease can progress and cause severe headache, nausea and breathing difficulty. Severe cases can cause acute respiratory distress syndrome, kidney failure, and even death. (Read about "Acute Respiratory Distress Syndrome")

  Rodent control in and around the home remains the primary strategy for preventing hantavirus infection at home, according to CDC. CDC says you should regularly check in and around your home for signs of rodent droppings or nests. You should also seal any holes where rodents can enter the home.

  HPS is also an issue for campers, as they pitch their tents in wooded areas and may sleep on the ground. Campers are advised to avoid setting up tents or sleeping bags in areas with rodent droppings. They should also take care to keep food stored in tightly sealed containers and to drink only disinfected water.

• Astroviruses - cause sporadic gastroenteritis in children under 4 years of age and account for about 4 percent of the children hospitalized for diarrhea. Most American children over 10 years of age have antibodies to the virus. (Read about "Gastroenteritis" "Diarrhea")
• Enteric adenovirus - causes 5-20 percent of the gastroenteritis in young children, and is the second most common cause of gastroenteritis in this age group. By 4 years of age, 85 percent of all children have developed immunity to the disease.
• Parvo-like viruses - have been implicated in a number of shellfish-associated outbreaks. FDA says the frequency of disease caused by parvo-like viruses is unknown. FDA also says parvoviruses infect all age groups and probably do not generate a permanent immunity.

Fungi

There are many, many different kinds of fungi, but only a small number of them make us sick. A fungus is actually a primitive plant that is found in air, in soil, on plants and in water. Some common fungi include mushrooms, yeast, mold and mildew. The body normally hosts a variety of fungi. Some of these are useful to the body, but others may form infections. A fungal infection of humans is called a mycosis. Mycoses can affect skin, nails, hair and internal organs. Some examples of common fungal infections include:

• athlete's foot (Read about "Tinea")
• diaper rash (Read about "Diaper Rash")
• jock itch (Read about "Tinea")
• ringworm (Read about "Tinea")
• thrush (Read about "Thrush")
• vaginal yeast infections (Read about "Vaginal Yeast Infections")

Other fungal infections may affect internal organs such as the lungs. Some examples of fungal lung infections are:

• Aspergillosis - a lung infection produced by inhaling a type of fungal spore. It produces fever, cough and chest pain and is associated with dust exposure. It is very common and is found in soil, decomposing plant matter, household dust, building materials, ornamental plants, items of food and water.
• Histoplasmosis - is an infection caused by inhaling the spores of a fungus that lives in soil, and bat or bird droppings. It is characterized by fever, chest pains and a dry cough.
• Coccidioidomycosis - is commonly called Valley fever and is caused by inhaling the spores of a fungus that lives in the soil of semiarid areas. It produces a flu-like illness with fever, cough, headaches and a rash.

People with compromised immune systems such as HIV infection or chronic lung disease are particularly at risk from these types of respiratory fungal infections. (Read about "The Immune System" "Chronic Obstructive Pulmonary Disease")

Protozoa

Protozoa are a group of microscopic, single-celled animals. They can be free-living or parasitic in nature. While protozoa can be an important source of food for animals like snails, clams and sponges, they can also cause serious infections in humans. Protozoa can be transmitted to the body by eating contaminated food or water, person-to-person contact, or through the bite of an insect like a mosquito or fly. While many protozoan infections are more common in the tropics and subtropics, they can also affect people in temperate zones as well. Some common examples of protozoa illnesses are:

• malaria (Read about "Travel & Health")
• giardiasis (Read about "Giardiasis")
• cryptosporidiosis (Read about "Cryptosporidiosis")
• toxoplasmosis (Read about "Toxoplasmosis")
• trichomoniasis (Read about "STD's")

Protect yourself

The best way to protect yourself from germs is to steer clear of the things that can spread them. Cover your nose and mouth when you sneeze and cover your mouth when you cough to keep from spreading germs. Remember the two words germs fear - soap and water. According to the Centers for Disease Control and Prevention, washing your hands with soap and water is one of the best ways to prevent infectious disease. Wash your hands every time you cough or sneeze, before you eat or prepare foods, after you use the bathroom, after you touch animals and pets, after you play outside and after you visit a sick friend or relative. Boil water if you don't know that is it safe to consume and make sure food is fresh and has been stored properly. (Read about "Food Safety")