Infectious Disease: Evolving Challenges to Human Health
WHERE ARE THEY?

Where Are They Interactive -- Text-only Version

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Bacteria

Location: Mouth
Common Name: Dental Plaque
Organism Names: Streptococcus mitis, S. oralis, S. gotdonii, S. sanguis, S. parasanguis, S. salivarius, S. mutans, Abiotrophia defectives, A. adjacens, Gemella haemolysans, Staphylococcus epidermidis, Staph. haemolyticus, Fusobacterium nucleatum, Haemophilus parainfluenzae, Lautropia mirabilis, Nesseria flavescens, N. macaca, Eikenella corrodens, Cardiobacterium hominis, Capylobacter gracilis, C. rectus, C. Concisus, Prevotella nigrescens, P. denticola, Capnocytophaga ochracea, C. granulose, Clostridia-group, Actinobacteria, and many more.
Organism Type: Bacteria
Danger to Humans: Commensal, Pathogenic, Unknown Description: The mouth is colonized with hundreds of different bacteria species. These bacteria make up a complex ecosystem that is established in infancy. Most of the bacteria are not pathogenic under most circumstances, but can cause dental caries (or cavities) on tooth enamel. One type of bacteria, Streptococcus mutans, converts sugars and starches into acids, which dissolve the surface of the tooth. Once a cavity has started other bacteria move in and make the hole larger.
Caption: Different bacterial communities can be seen in this photo of tooth enamel taken 8 hours after brushing. The bacteria have been stained with different fluorescent dyes to make them stand out. (Paul E. Kolenbrander and Robert J. Palmer, Jr. Revised version of figure published in: Palmer, R. J., Jr., S. Gordon, J. O. Cisar, and P. E. Kolenbrander. 2003. J. Bacteriol. 185:3400-3409.)

Location: Intestine
Common Name: Cholera
Organism Name: Vibrio cholerae
Organism Type: Bacteria
Danger to Humans: Pathogen
Description: Cholera is a life-threatening diarrheal disease that is found in areas with poor sanitation and in coastal environments near brackish water. Although it is asymptomatic in most people, about 5% of the cases are severe and can cause death within hours without treatment. Cholera can be treated with antibiotics, but the most effective therapy is oral rehydration with salt and water to replace the fluids and essential salts lost because of diarrhea. Cholera can be avoided by drinking purified or boiled water and by avoiding potentially contaminated seafood.
Caption: A photo of Vibrio cholerae taken with a scanning electron microscope. It is magnified 22,371 times its actual size. (CDC/Janice Carr)

Location: Intestine
Common Name: Bacterial Ecosystem
Organism names: Bacteroides vulgatus, B. thetaiotomicron, Bifidobacterium longum, Clostridium spp., Enterococcus faecalis, Escherichia coli, Eubacterium spp., E. rectale, Faecalibacterium prausnitzii, Firmicutes, Prevotella spp., and more than 100 others
Organism Type: Bacteria
Danger to Humans: Commensal/Pathogenic/Unknown
Description: The human intestine is home to a one of the densest ecosystems on the planet. Over 100 trillion microbes live inside every adult’s gut. Two divisions of bacteria, the Bacteriodes and the Firmicutes, dominate this ecosystem making up about 60% of all of the bacteria in the digestive system. The bacterial ecosystem can be beneficial by breaking down complex sugars, which might not otherwise be digested. Competition between bacteria may also keep potentially pathogenic bacteria in check so they do not cause harm.
Caption: Bacteroides hypermegas is part of the normal flora in the human intestine. (CDC/Dr. V. R. Dowell, Jr.)

Location: Stomach
Common Name: Peptic Ulcers
Organism Name: Helicobacter pylori
Organism Type: Bacteria
Danger to Humans: Pathogenic
Description: An ulcer is a sore in the lining of the stomach or the small intestine. More than 25 million Americans will suffer from ulcers in their lifetime. Once thought to be caused by spicy foods or stress, most ulcers are now attributed to Heliobacter pylori bacteria. The bacteria weaken the mucous coating of the stomach allowing digestive acid to irritate its sensitive lining. Ulcers caused by H. pylori can be treated with antibiotics and an acid-suppressor.
Caption: A photo of a cluster of H. pylori a common cause of stomach ulcers. The bacteria has been colored pink in this image. (Image copyright Dennis Kunkel Microscopy, Inc.)

Location: Lung
Common Name: Pneumonia
Organism names: Chlamydophila pneumoniae, Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae type B
Organism Type: Bacteria
Danger to Humans: Pathogenic
Description: Approximately 5% - 10% of children in developing countries suffer from bacterial pneumonia each year. This acute respiratory infection can be caused by several different bacteria and is characterized by fast, difficult breathing and coughing caused by inflammation of the lungs. Acute, respiratory infections cause more than 2 million deaths in children worldwide, most in infants less than 1 year of age. In the United States, antibiotics can be used to cure infections and vaccines for H. influenzae type B and S. pneumoniae offer protection against infection with these organisms.
Caption: Photo of a Streptococcus pneumoniae taken with a scanning electron microscope. (CDC/Dr. Richard Facklam)

Location: On ladder
Common Name: Strep Throat, Flesh Eating Bacteria
Organism Name: Streptococcus pyogenes
Organism Type: Bacteria
Danger to Humans: Pathogenic
Description: Streptococcus pyogenes is a group A streptococcus (GAS) that can produce a variety of toxins. Infection normally is asymptomatic or causes a mild illness, but can be life-threatening in rare cases. If toxin-producing bacteria get into blood, muscle, or lungs, they can cause a serious illness known as “invasive GAS disease.” The two most severe forms of invasive GAS disease are necrotizing fasciitis, which has been called “flesh eating bacteria,” and Streptococcal toxic shock syndrome. About 20% of patients with necrotizing fasciitis and more than half with toxic shock die.
Caption: In this micrograph of Streptococcus pyogenes, the bacteria appear as strings of red pearls. It is magnified 900 times its actual size. (CDC)


Location: Hands
Common Name: Skin and Internal Organs Abscesses
Organism Name: Staphylococcus aureus
Organism Type: Bacteria
Danger to Humans: Pathogenic
Description: Staphylococcus aureus lives on the skin of most healthy people. Typically is does not cause disease, but it can cause abscesses and life-threatening illnesses such as wound infections and toxic shock syndrome, if it grows out of control or in the wrong location. The development of antibiotic resistance in S. aureus has made this once easy to treat infection a growing threat.
Caption: A photo of Staplylococcus aureus taken with a scanning electron microscope and it magnified 9560 times its actual size. (CDC/Janice Carr; Jeff Hageman, M.H.S.)

Location: Yogurt
Common Name: Normal Flora
Organism Name: Lactobacillus acidophilus
Organism Type: Bacteria
Danger to Humans: Commensal
Description: Lactobacillus acidophilus is a “friendly” or commensal bacterium. It converts the sugar lactose into lactic acid. It is used to make yogurt, lactose-free milk and other fermented milk products. In the intestine, it may also help to boost the immune system and have other benefits. In the vagina it is part of the natural microbial community and helps halt yeast infections.
Caption: Lactobacillus acidophilus is used to make lactose-free products such as milk and cheese. (USDA ARS)

Location: Intestine
Common Name: E. coli
Organism Name: Escherichia coli
Organism Type: Bacteria
Danger to Humans: Commensal or Pathogenic
Description: There are hundreds of varieties of E. coli. It is a natural part of the intestinal ecosystem and usually causes no problems. However, if it leaves the intestinal tract and gets into other areas of the body, it can cause disease. Certain strains of E. coli, such as E. coli 0157:H7, are normally associated with contaminated food and produce toxins that can cause food poisoning and fatal disease, particularly in small children.
Caption: E. coli is used for many common laboratory studies, but certain strains can be dangerous. (USDA ARS)

Location: Lungs
Common Name: Tuberculosis, TB
Organism Name: Mycobacterium tuberculosis
Organism Type: Bacteria
Danger to Humans: Pathogenic
Description: Although most cases are asymptomatic, one third of the world’s population is infected by M. tuberculosis. Every second, someone in the world is infected when a carrier spreads the bacteria by coughing, sneezing, talking or spitting.. Tuberculosis can cause coughing and wasting leading to death. The bacteria are slow growing and patients must take multiple antibiotics for 6 months or more to be cured. The spread of multi-drug resistant tuberculosis is a serious and emerging problem world-wide.
Caption: Magnified over 15,000 times its actual size, Mycobacterium tuberculosis is shown in the scanning electron micrograph. (CDC/Dr. Ray Butler; Janice Carr)

Location: Intestine
Common Name: Food-Poisoning, Diarrhea
Organism Name: Campylobacter jejuni
Organism Type: Bacteria
Danger to Humans: Pathogenic
Description: Campylobacter is one of the most common bacterial causes of intestinal disease in the United States. It causes fever, abdominal cramping, and diarrhea. More than half of the chickens in the United States have Campylobacter infections, but are not sick. In humans, disease usually occurs in single sporadic cases, caused by eating food contaminated with the bacteria. This form of food poising can be avoided through proper food handling and preparation, such as using separate cutting surfaces for raw foods and meats and not undercooking food.
Caption: A common cause of intestinal illness, this photo shows Campylobacter jejuni taken with a scanning electron microscope. (CDC/Dr. Patricia Fields; Dr. Collette Fitzgerald)

Location: Intestine
Common Name: Salmonellosis, Diarrhea
Organism Name: Salmonella
Organism Type: Bacteria
Danger to Humans: Pathogenic
Description: Salmonella can cause diarrhea, fever, and abdominal cramps. Most people recover in 4 to 7 days, but it can be more serious and even fatal in infants and the elderly. Salmonella is transmitted to humans by eating foods, usually meat, contaminated with the bacteria, but can also be transmitted via unwashed hands. Reptiles also harbor Salmonella, which is why the CDC recommends that children under 5 years of age and immunocompromised persons not handle pet turtles and other reptiles.
Caption: A photo of Salmonella infantis, one of the strains that cause Salmonellosis, taken with a scanning electron microscope. (CDC/Janice Carr)

Location: Face
Common Name: Acne
Organism Name: Propionibacteri acnes
Organism Type: Bacteria
Danger to Humans: Pathogenic
Description: Most Propionibacteri are non-pathogenic. One variety is even used to make the holes in Swiss cheese. However, some varieties can cause infection. Propionibacteri acnes, for example, causes of skin acne. It can normally be cured with over the counter soaps and antiseptics.
Caption: A photo of Propionibacteri acnes. (CDC/Bobby Strong)

Location: Hand
Common Name: Normal Flora
Organism Name: Staphylococcus epidermidis
Organism Type: Bacteria
Danger to Humans: Commensal or Pathogenic
Description: Staphylococcus epidermidis is part of the normal bacteria flora found on the skin. It is normally harmless, but can cause infection in immune-compromised patients and in patients with medical devices implanted. In medical settings, it is part of the biofilm, or slime, that can form on medical devices such as catheters and can be very difficult to treat with antibiotics.
Caption: A photo of a Staphylococcus biofilm on a medical device taken with a scanning electron microscope. (CDC/Dr. Rodney M. Donlan)

Location: Soil
Common Name: Streptomyces
Organism Name: Streptomyces
Organism Type: Bacteria
Danger to Humans: Harmless
Description: Streptomyces typically lives in the soil or decaying leaves. They have a distinctive “earthy” odor. Streptomyces produce a large number of antibiotics including Streptomycin.
Caption: Colonies of Streptomyces, the source of many antibiotics. (John Innes Centre - www.jic.ac.uk)

Viruses

Location: Blood, Lungs, Kidneys
Common Name: CMV
Organism Name: Cytomegalovirus
Organism Type: Virus
Danger to Humans: Pathogenic
Description: Cytomegalovirus is a common virus that infects the majority of people over 40 years old in the United States. Most people never know they have the infection, which causes mild symptoms and remains latent or silent in blood cells for the life of the person. If a woman is first infected with cytomegalovirus during pregnancy then she has a 30% chance of passing the infection onto her unborn child, which can result in permanent mental and physical disability. Transmission occurs through close contact with body fluids and can be avoided through good hygiene.
Caption: Photo of a cell in urine infected with cytomegalovirus. (CDC/Dr. Haraszti)

Location: Nose
Common Name: Common Cold, Conjunctivitis
Organism Name: Adenovirus
Organism Type: Viruss
Danger to Humans: Pathogen
Description: Respiratory adenoviruses cause a range of diseases from the common cold to bronchitis and pneumonia. They may also cause conjunctivitis. Most infections are mild and patients recover in 4 to 7 days. Adenoviruses are being engineered for gene therapy and for new types of vaccines.
Caption: Photo of adenovirus taken with a transmission electron microscope. (CDC/Dr. G. William Gary, Jr.)

Location: Nose
Common Name: Common Cold
Organism Name: Rhinovirus
Organism Type: Virus
Danger to Humans: Pathogen
Description: Rhinoviruses cause more than 50% of all colds, making it the most common viral infective agent. The virus causes fever, coughing and nasal congestion. Rhinovirus spreads through droplets in the air and on hands. Currently, there is no cure for the common cold and most patients recover in 3 to 5 days.
Caption: Image of rhinovirus 16. The image has been colored to highlight the structures that make up the virus's protein shell (Image courtesy of J.-Y. Sgro, UW-Madison, from data in PDB-ID: 1AYM, Hadfield et al. (1997) Structure 5:427-441, http://virology.wisc.edu/virusworld)

Location: Blood (B Lymphocytes)
Common Name: Infectious Mononucleosis, Mono
Organism Name: Epstein-Barr Virus
Organism Type: Virus
Danger to Humans: Pathogen
Description: As many as 95% of the adults in the United States have been infected with Epstein-Barr virus. The virus passes from person to person through exposure to saliva, which is why it is nicknamed “the kissing disease.” Infection with the virus in teenagers or young adults causes mononucleosis and the infected person shows symptoms of fever, sore throat, and swollen lymph glands. Younger children often have fewer symptoms.
Caption: Epstein-Barr Virus is transmitted from person to person through exposure to saliva, such as through a kiss.

Location: Lungs
Common Name: Influenza, Flu
Organism Name: Influenza Virus Types A & B
Organism Type: Virus
Danger to Humans: Pathogen
Description: Each year slightly different strains of influenza virus types A and B circulate around the world causing respiratory disease in the winter months. Symptoms include nasal congestion, coughing, muscle aches and fever. Although most people recover from the flu, it can be fatal, causing 36,000 deaths in the United States each year. The best prevention is the yearly flu vaccine. Waterbirds are the natural reservoir for influenza A viruses. Several times each century, a human influenza virus moves from birds to humans or recombines with an avian virus to create a strain of influenza that has never been seen before in humans. This can cause a global outbreak or pandemic, such as occurred in 1918.
Caption: A photo of an influenza virus taken with a transmission electron microscope. Internal details can be seen. (CDC/Dr. Erskine Palmer; Dr. M. L. Martin)

Location: Lungs
Common Name: Bird Flu, Avian Influenza
Organism Name: Avian Influenza Type A (H5N1)
Organism Type: Virus
Danger to Humans: Pathogen
Description: Influenza A viruses circulate not only in humans, but also in birds, pigs, horses and seals and the natural reservoir is in waterfowl. Typically, the influenza viruses in animals do not infect humans, but occasionally an animal virus either mutates or recombines with a human virus to create a strain that will infect humans. This can cause a world-wide influenza pandemic in humans because it is a new strain to which no one is immune. Scientists have been monitoring the H5N1 avian influenza virus because it has caused severe disease in domestic poultry and there have been several human cases.
Caption: A photo of an avian influenza H5N1 virus particle magnified 150,000 times actual size with a transmission electron microscope. (CDC/Cynthia Goldsmith; Jackie Katz)

Location: Gut
Common Name: Gastroenteritis, Winter Vomiting Disease
Organism Name: Norwalk Virus
Organism Type: Virus
Danger to Humans: Pathogen
Description: Norwalk and related virus infections are the most common food-borne illness in the United States and often occur as outbreaks of intestinal illness in schools, nursing homes and on cruise ships. It is spread through the feces of an infected person. Sick food handlers with unwashed hands or shellfish that has been contaminated with raw sewage are common sources of the infection. Symptoms include nausea, vomiting, stomach cramps and diarrhea.
Caption: X-ray structure of the Norwalk virus capsid. The structure has been colored to highlight the three domains of the capsid protein. (B.V.Venkataram Prasad, Baylor College of Medicine)

Location: Immune Cells
Common Name: AIDS (Acquired Immune Deficiency Syndrome)
Organism Name: Human Immunodeficiency Virus (HIV)
Organism Type: Virus
Danger to Humans: Pathogen
Description: Human Immunodeficiency Virus (HIV) was first identified in the 1980’s and has become a worldwide pandemic. HIV infects lymphocytes and causes the Acquired Immune Deficiency Syndrome (AIDS) that destroys person’s immune system. Anti-retroviral drugs can extend the life of a person with HIV, but it cannot be cured because the virus integrates itself into the genome of the infected cells. Prevention remains the only way to remain virus-free. In 2005, 40 million people were infected and more than 3 million died of this incurable disease.
Caption: In this photo taken with a scanning electron microscope, HIV can clearly be seen on the surface of a human lymphocyte. (CDC/C. Goldsmith; P. Feorino; E. L. Palmer; W. R. McManus)

Location: Gut
Common Name: Diarrhea
Organism Name: Rotavirus
Organism Type: Virus
Danger to Humans: Pathogen
Description: More than 600,000 children world-wide die due to rotavirus infection each year. It is the most common cause of severe dehydrating diarrhea among young children. The incubation period of the disease is 2 days followed by 3 to 8 days of vomiting and watery diarrhea. Treatment is oral rehydration solution. The FDA approved a new rotavirus vaccine for use in children in 2006.
Caption: A 3-D reconstruction of Rotavirus using cryo-electron micrographs. The image has been colored to highlight the spikes, outer and inner capsid layers. (B.V.Venkataram Prasad, Baylor College of Medicine)

Location: Liver
Common Name: Hepatitis, Liver Cirrhosis, Liver Cancer
Organism Name: Hepatitis B Virus (HBV)
Organism Type: Virus
Danger to Humans: Pathogen
Description: Hepatitis B virus infects liver cells and can cause inflammation in the liver, which results in jaundice, extreme fatigue, nausea, and stomach pain. Of the 2 billion people world-wide that have been infected, 350 million have chronic (life-long) infections. A chronic infection can result in cirrhosis of the liver, liver cancer and even death. Infection with Hepatitis B virus is preventable with a vaccine that has been available since the early 1980’s. This vaccine is increasingly available in the developing world where the majority of infections occur.
Caption: A photo of Hepatitis B virus taken with a transmission electron microscope. (CDC/Dr. Erskine Palmer)

Location: Liver
Common Name: Hepatitis, Liver Cirrhosis, Liver Cancer
Organism Name: Hepatitis C Virus
Organism Type: Virus
Danger to Humans: Pathogen
Description: Most people who are infected with Hepatitis C virus never know it because infection is asymptomatic in 90% of cases. About 20 -30% of infected persons clear the virus while the remaining 130 million people, about 3% of the world’s population, develop chronic (life-long) infection. A chronic infection can result in cirrhosis of the liver or liver cancer. Hepatitis C virus infection is responsible for 50-75% of all liver cancer and most liver transplants.
Caption: A photo of Hepatitis C virus taken with a transmission electron microscope. The virus has been false colored to appear blue. (Image copyright Dennis Kunkel Microscopy, Inc.)

Location: Mouth
Common Name: Cold Sores
Organism Name: Herpes Simplex Type 1
Organism Type: Virus
Danger to Humans: Pathogen
Description: Herpes simplex type 1 causes blisters in the mouth and on the face. The virus is present in saliva and most people are infected during childhood. 90% of all adults have been infected with herpes simplex type 1 at some point in their lives. After infection, the virus becomes latent in nerve cells where it can become active again and move down the nerve processes to cause recurrent cold sores or fever blisters.
Caption: A close-up of a cold sore on the lower lip caused by the Herpes Simplex Type 1 virus. (CDC/ Dr. Hermann)

Location: Blood, Skin
Common Name: Chicken Pox, Shingles
Organism Name: Varicella Zoster Virus
Organism Type: Virus
Danger to Humans: Pathogen
Description: Chicken pox can now be prevented with the varicella vaccine. Before the vaccine was licensed, almost every child in the United States was infected with varicella zoster virus before the age of 15 and 50 - 100 children died each year from chicken pox. The disease is characterized by a blister-like rash, tiredness, and fever. Chicken pox is highly infectious and can spread through the air or by contact with the blisters. After recovery, the virus remains latent in nerve cells located along the spine and many years later can become active decades later, causing shingles or zoster along the path of one group of nerve cells.
Caption: Lesions on the body of a young boy with chicken pox. (CDC/J.D. Millar)

Location: Brain
Common Name: West Nile Fever, Encephalitis
Organism Name: West Nile Virus
Organism Type: Virus
Danger to Humans: Pathogen
Description: West Nile virus first appeared in the United States in 1999. Since then it has spread from the New York City area to all of the 48 contiguous states. West Nile virus infects mosquitoes and birds and can be transmitted to humans with a single mosquito bite. Most people who are infected have no symptoms. 20% of the people infected will have mild symptoms including fever, headache and a skin rash. One in every 150 persons will have severe symptoms associated with infection of the brain that can result in paralysis.
Caption: A surface view of West Nile Virus. The image was produced using cryo-electron microscopy and image reconstruction techniques (Richard J. Kuhn, Purdue University).

Location: Blood, Liver
Common Name: Yellow Fever
Organism Name: Yellow Fever Virus
Organism Type: Virus
Danger to Humans: Pathogen
Description: Historically, the yellow fever virus has caused severe epidemics. Symptoms for this presently incurable disease range from headaches, to jaundice caused by liver failure, and black vomit from hemorrhaging of the digestive tract. It can even cause delirium, coma, and death. It is transmitted by mosquitoes in the tropical areas of Africa and South America. Although an effective vaccine is available for yellow fever, it still causes 30,000 deaths worldwide each year.
Caption: Yellow fever virus is carried by the day-biting Aedes aegypti mosquito, which prefers to feed on humans. (CDC/James Gathany)

Location: Lungs
Common Name: Bronchitis, Pneumonia, Croup
Organism Name: Respiratory Syncytial Virus (RSV)
Organism Type: Virus
Danger to Humans: Pathogen
Description: Respiratory syncytial virus is the most common cause of bronchitis and pneumonia among infants under 1 year of age. Most children have symptoms of fever, runny nose, coughing, and wheezing. Some children require hospitalization. It is possible to be re-infected with RSV at any age.
Caption: A photo of respiratory syncytial virus taken with an electron scanning microscope. (CDC)

Location: Cervix
Common Name: Warts
Organism Name: Human Papilloma Virus (HPV)
Organism Type: Virus
Danger to Humans: Pathogen
Description: There are more than 50 types of human papilloma virus (HPV). Some cause warts on the skin and others cause genital infections, which are sexually transmitted diseases. HPVs causing warts can be passed by touching and disappear after a few months or years or can be removed. Certain genital HPV types are the major cause of cervical cancer and are referred to as “high-risk.” The FDA recently approved a vaccine for two of the “high-risk” types that cause more than 70% of all cervical cancers in the United States.
Caption: A 3-D reconstruction of a Human Papilloma Virus particle, from cryo-electron microscopy and x-ray crystallography. The image has been colored to highlight the structure of the outer capsid layer of the virus. (Stephen C. Harrison, Harvard Medical School

Location: Blood, Skin
Common Name: Measles
Organism Name: Measles Virus
Organism Type: Virus
Danger to Humans: Pathogen
Description: Measles is one of the most contagious known diseases. Almost all non-immune children will be infected if exposed to the virus. Symptoms include runny nose, fever and rash. Children do not normally die of measles, but from its complications, which include encephalitis, pneumonia, and blindness. In the United States, most people are vaccinated against measles and outbreaks occur in small, unvaccinated communities. World-wide, more than 450,000 people, mostly children, die of measles each year where vaccine coverage is much lower.
Caption: A child displaying the characteristic blotchy patches seen on the third day of a measles infection. (CDC)

Location: Salivary Glands
Common Name: Mumps
Organism Name: Mumps Virus, Paramyxovirus
Organism Type: Virus
Danger to Humans: Pathogen
Description: Mumps is a mild childhood disease caused by virus infection of the salivary gland. Symptoms include swelling of the salivary glands, weakness, and fever. Although it is a mild disease in children, adult infections can involve other glands, such as the pancreas, ovaries and testes, and may lead to complications including male sterility.
Caption: A photo of the mumps virus taken with a transmission electron microscope. (CDC/ Dr. F. A. Murphy)

Fungi

Location: Nose, Lungs
Common Name: Mold
Organism Name: Aspergillus fumigatus
Organism Type: Fungus
Danger to Humans: Pathogen
Description: Aspergillus can cause a wide range of illnesses from allergic reactions to life-threatening infections. The mildest disease is caused by allergies to the mold spores, which leads to symptoms similar to asthma. In some patients, Aspergillus can grow in the lungs or sinuses. The most serious condition occurs in immunocompromised individuals when Aspergillus infects the blood, leading to fungal growth throughout the body and even in the brain. Aspergillus infections can be treated with anti-fungal medication.
Caption: A microscopic photo of Aspergillus fumigatus showing its spores. (CDC)

Location: Foot
Common Name: Tinea unguium, Onychomycosis (Nail Fungus)
Organism Name: Microsporum, Epidermophyton and Trichophyton
Organism Type: Fungus
Danger to Humans: Pathogen
Description: Onychomycosis, an infection of the nails, is caused by a variety of different fungi. It primarily affects older adults. The symptoms range from discoloration of the nails to total nail destruction. It often results from untreated Tinea pedia (Athlete’s foot). Mild cases can be cured with topical anti-fungal medication, but more serious cases require oral anti-fungal medication.
Caption: A fungal infection of the nails by Trichophyton rubrum causes the nails to become discolored and brittle. (Courtesy of www.doctorfungus.org © 2006)

Location: Foot
Common Name: Athlete’s Foot (Tinea pedis)
Organism Name: Microsporum, Epidermophyton and Trichophyton
Organism Type: Fungus
Danger to Humans: Harmless or Pathogen
Description: Athlete’s foot can be caused by a variety of fungi including Microsporum, Epidermophyton and Trichophyton. Typically harmless, these fungi live on the skin and feed on dead cells. Under the right conditions the fungi can infect the skin and cause a variety of symptoms including itchiness, redness, and even blisters. Most athlete’s foot is cured by topical medications.
Caption: A colony of Trichophyton mentagrophytes var. erinacei, one the varieties of fungus that can cause Athlete’s foot. (Courtesy of www.doctorfungus.org © 2006)

Location: Skin
Common Name: Ringworm (Tinea corporis)
Organism Name: Microsporum, Epidermophyton and Trichophyton
Organism Type: Fungus
Danger to Humans: Harmless or Pathogen
Description: Ringworm is not cause by a worm but by fungus. Normally the fungus lives on the skin eating dead cells and is harmless. If it infects cells it can cause raised red itchy or scaly patches on the skin. It is easily spread through direct skin to skin contact or through contaminated objects such as damp towels. Ringworm can normally be cured with over the counter medications.
Caption: Ringworm (Tinea corporis) on the arm of a patient. (CDC/Dr. Lucille K. Georg)

Location: Mouth, Skin, Genital Tract
Common Name: Oral Thrush, Vaginal Yeast Infection
Organism Name: Candida albicans
Organism Type: Fungus
Danger to Humans: Harmless or Pathogen
Description: Candida albicans is a yeast that lives in the mouth and gut of most people. Environmental cues can change it from its typical unicellular form to a filamentous form that can invade tissues. Candida albicans can infect the mouth, where it is called thrush; or the vagina, where it causes vaginal yeast infections; or moist skin, where it causes skin rashes such as diaper rash. It is particularly dangerous to immunocompromised patients, such as people with AIDS.
Caption: A micrograph of Candida albicans. (CDC/Dr. Godon Roberstad)

Location: Lung, Brain
Common Name: Valley Fever, Coccidioidomycosis
Organism Name: Coccidioides immitis
Organism Type: Fungus
Danger to Humans: Pathogen
Description: Coccidioides immitis and the related Coccidioides posadasii are found in Southern California and the deserts of the U.S. Southwest, Mexico and South America. They can cause coccidioidomycosis when the spores of the fungus are inhaled and infect the lungs. In about 50% of the patients the infection is asymptomatic, but in the remaining patients symptoms can range from pneumonia to meningitis. Outbreaks occur when the earth has been disturbed such after a dust storm or earthquake.
Caption: A culture of Coccidiodes immitis grown in a culture dish. (Courtesy of www.doctorfungus.org © 2006)

Location: Lungs, Blood
Common Name: Blastomycosis
Organism Name: Blastomyces dermatitidis
Organism Type: Fungus
Danger to Humans: Pathogen
Description: An uncommon disease, blastomycosis occurs when the spores of the fungus Blastomyces dermatitidis are inhaled. The fungus then grows inside the lungs and can spread to other organs. This can cause a range of symptoms from coughing blood to weight loss. B. dermatitidis is found in moist, organic soil and most people are infected when the soil is disturbed and they inhale spores. In the U.S., the fungus is found in the southeastern United States, particularly in the Mississippi and Ohio River valleys and around the Great Lakes states. Blastomycosis can be treated with anti-fungal medication.
Caption: A chest x-ray of a patient with blastomycosis. The fungus can be seen as the white fuzzy area on the right lung. (Courtesy of www.doctorfungus.org © 2006)

Location: Lungs
Common Name: Histoplasmosis
Organism Name: Histoplasma capsulatum
Organism Type: Fungus
Danger to Humans: Pathogen
Description: Histoplasma capsulatum is found often in soil contaminated with bat or bird droppings. 90% of infected persons will have no symptoms. However, it can spread throughout the body causing high fever, headache, cough, chills, weakness, and chest pain in some patients. Since the advent of the HIV epidemic, histoplasmosis has reemerged to become one of the most opportunistic diseases in those areas of the world endemic to this soil-based fungus, predominately river valleys in North and Central America.
Caption: A culture of Histoplasma capsulatum that had been isolated from a patient’s blood then grown in culture. (Courtesy of www.doctorfungus.org © 2006)

Parasites

Location: Rectum, Anus
Common Name: Pin Worm
Organism Name: Enterobius vermicularis
Organism Type: Parasite
Danger to Humans: Pathogen
Description: Pin worms are small worms about the size of staples. They live in the human rectum and at night the female pin worm exits the anus to lay eggs. This can be itchy and disturb sleep. Loss of appetite can occur in extreme cases. Pin worm is the most common worm infection in the United States. It infects mostly children and can spread through institutional settings such as schools and day care centers. Good personal hygiene, particularly after going to the bathroom, can help stop the spread of the worm.
Caption: Pin worms are often diagnosed by the presence of eggs seen in this photo. (CDC)

Location: Intestine
Common Name: Beef Tapeworm
Organism Name: Taenia saginata
Organism Type: Parasite
Danger to Humans: PathogenDescription: Taenia saginata infects both cows and humans, but can only reproduce in humans. Because of this, it occurs where cattle are raised and human feces are improperly disposed. Humans become infected by eating undercooked beef. Symptoms include loss of appetite, nausea, vomiting, and diarrhea. The parasite is commonly found in Africa, Latin America, the Philippines, and Eastern Europe.
Caption: The adult beef tapeworm can grow to 15 feet long. (CDC)

Location: Liver, Intestine
Common Name: Liver Fluke
Organism Name: Fasciola hepatica
Organism Type: Parasite
Danger to Humans: Pathogen
Description: Liver flukes typically infect cows, sheep, and other ruminants that graze in marshy areas, but they can also infect humans who eat vegetation grown in contaminated water, such as watercress. The liver fluke burrows through the lining of the intestine and then feeds on the liver. The fluke can cause a variety of symptoms including anemia and malaise.
Caption: The liver fluke is a parasitic flatworm. (Image courtesy of BIODIDAC)

Location: Blood, Brain
Common Name: Toxoplasmosis
Organism Name: Toxoplasma gondii
Organism Type: Parasite
Danger to Humans: Pathogen
Description: More than 60 million people in the United States may be infected with Toxoplasma gondii. Most people have no symptoms because their immune system keeps the parasite at bay. The parasite can be a serious problem in immunocompromised patients and in pregnant woman since an infected newborn may have eye or brain damage. Toxoplasma gondii-infected cats shed an infectious form of the parasite in feces. The parasite can be ingested after cleaning cat litter boxes, gardening or eating partially cooked meat. Good hygiene and wearing gloves can help to prevent infection.
Caption: A "rosette" of replicating Toxoplasma gondii parasites. The green color is staining of the major surface protein captured by fluorescence microscopy. (David Sibley)

Location: Liver, Blood
Common Name: Malaria
Organism Name: Plasmodium falciparum, P. vivax, P. malariae, P. ovale
Organism Type: Parasite
Danger to Humans: Pathogen
Description: Malaria is a preventable and curable disease, yet 1 million people die of malaria each year, most of them children. The malaria parasite has two hosts: humans and female Anopheles mosquitoes. When infected mosquitoes feed, they can inject the malaria parasite into the blood. Once in the human host, the parasite multiplies in the liver and then in red blood cells. This can cause fevers, chills, and anemia, as well as cerebral malaria and death. Malaria can be prevented by avoiding mosquito bites or by taking anti-malarial drugs (prophylaxis) and can be cured using anti-malarial drugs.
Caption: Photo of malaria parasite in its sexual stage. This stage is found in human blood. (CDC)

Location: Intestine, Muscles
Common Name: Roundworm
Organism Name: Toxocara felis (cats), Toxocara canis (dogs)
Organism Type: Parasite
Danger to Humans: Pathogen
Description: Toxocara typically live in the intestines of dogs and cats. Eggs are shed in the feces and can live in the soil for many years. Humans can be infected if they accidentally ingest eggs when eating with contaminated hands. Once in the intestine, the eggs quickly hatch and the larva burrow through the intestine wall to enter the liver, muscles and lungs. The severity of the infection depends on the number of eggs eaten. Symptoms include rash, difficulty breathing, abdominal pain, and in the most severe cases, brain damage.
Caption: Humans can be infected with Toxocara cati when they eat the eggs of the parasite. (Joel Mills)