Hygiene - Viruses, Bacteria, and Parasites

• Viruses are pieces of nucleic acid (DNA or RNA) wrapped in a thin coat of protein that replicate only within the cells of living hosts.
• Bacteria are one-cell microorganisms with a simple cellular organization whose nucleus lacks a membrane.
• Parasites may be protozoa, yeasts, or multicellular organisms such as fungi or worms that live in or on a host to obtain nourishment without providing any benefit to the host.

Hygiene
Hygiene is the science that deals with the promotion and preservation of health by reducing harmful levels of germs through cleanliness and sterilization. The two most common hygienic practices are: 1) washing hands and food preparation areas with soap, and 2) cooking food and boiling drinking water. Washing with soap removes oils and breaks up dirt particles so they may be washed away, whereas cooking and boiling kill harmful organisms that cannot be removed by washing. You can prevent diseases caused by viruses, bacteria, and parasites by keeping a clean environment and by handling food in a sanitary manner. Most intestinal parasites are transmitted by contact with feces from an infected person or pet. These are some of the most important sanitation practices to help you maintain your health:

• Wash your hands before cooking or eating.
• Wash your hands after using the bathroom, changing a child's diapers, shaking hands, handling money, touching door handles, elevator buttons, light switches, handrails in public places, and handling pets.
• Do not touch your eyes, nose, mouth, or any food after touching any contaminated surfaces until after you have washed your hands. Wear gloves to prevent contamination.
• Keep cutting boards and food preparation areas clean by washing them with soap and water and allowing them to dry thoroughly.
• Cook meats and seafood. Cooking to a temperature of 180°F (82°C) will kill disease-causing organisms. Use a meat thermometer when cooking roasts or whole turkeys to be sure food is cooked to a safe temperature.
• Keep raw food away from cooked food. Avoid cross-contamination by using separate plates for the cooked and the raw food.
• Drink purified water and use purified water for washing hands and cleaning food preparation areas. Water can be purified by boiling for a few minutes or by chemical treatments such as chlorination.
• Keep food refrigerated to delay spoilage. Low temperatures slow down reproduction of bacteria.
• Don't let cooked food sit at room temperature too long. Food should be promptly packed in shallow containers so it can chill quickly, and put in the refrigerator. Keeping food refrigerated at or below 4°C/40°F slows down bacterial growth.
• Vegetables that are eaten raw, such as carrots, lettuce, tomatoes, etc., should be washed thoroughly. The vinegar in some salad dressings will also kill many types of bacteria.
• Wash fruits that are cut, such as melons, to avoid transferring any dirt or contamination from the outside of the fruit to the inside during cutting.
• Do not eat spoiled food, or any food that has an unpleasant smell or taste. You cannot always see, smell or taste harmful organisms. When in doubt, throw out old food rather than risk getting sick.
• Breathe clean air. Avoid smoky, dusty, musty environments, or confined places where people are coughing or sneezing. Wearing a surgical face mask can reduce the chances of contracting or spreading diseases caused by infectious organisms carried in the droplets from coughing or sneezing.
• Avoid insect bites by using window screens, mosquito netting, insect repellents, and by being indoors between dusk and dawn when mosquitoes are most active. Many viral, bacterial, and protozoan diseases are transmitted by insect bites from mosquitoes, flies, fleas, and ticks. Diseases transmitted by mosquitoes include Dengue Fever, Malaria, Rift Valley Fever, Yellow Fever, and various types of viral encephalitis such as West Nile virus.
• Avoid walking barefoot on soil or swimming in water contaminated by feces. Hookworm and schistosomiasis infections start when the larvae penetrate the skin. It is possible to get parasites from cats and dogs. Test your pets for parasites regularly and dispose of their feces in a sanitary manner.
• To prevent wart infections and athlete's foot, avoid walking barefoot in public areas such as showers or communal changing rooms. Avoid sharing shoes and socks.
• Brush and floss your teeth every day before going to bed to prevent gum diseases and dental decay.
• Many diseases are transferred by close contact with an infected individual. Be very selective in your intimate personal relationships, and avoid touching any sores, feces, or body fluids from a sick person.

Viruses
Viruses penetrate the cell walls of body tissues bringing a payload of DNA or RNA that starts replicating the virus inside the infected cells. When the cell dies, multiple copies of the virus are released and continue to infect other cells. The human body sometimes is able to build antibodies that prevent the replication of the virus to stop the infection. Vaccines consist of weakened viruses that stimulate the body's defenses to fight infection by the natural viruses. Here is a list of diseases caused by viruses:

• Common Cold is caused by a rhinovirus
• Influenza (Flu) - Learn more about the Influenza Virus
• COVID-19 is a highly infectious corona virus transmitted by airborne particles.
• Dengue fever is transmitted by bites from mosquitoes mainly in Southeast Asia and South America
• Acquired Immunodeficiency Syndrome (AIDS) is caused by the Human Immunodeficiency Virus (HIV). It is transmitted by sexual contact with an infected person or by sharing needles or syringes for drug injection.
• Hepatitis (inflammation of the liver, jaundice)
• Herpes (cold sores, and genital herpes)
• Rabies (transmitted by bites from infected bats, raccoons, dogs)
• Polio (may cause paralysis)
• Smallpox (eradicated from the world in 1977 through vaccination)
• Mumps
• Yellow Fever is a viral hemorrhagic fever transmitted by infected mosquitoes.
• Measles or rubella
• Warts caused by a virus may be treated at home with solutions and patches containing salicylic acid over several weeks, or in the doctor's office by freezing.

Bacteria
Bacteria are one-celled organisms that do not have membranes binding their nuclear material (prokaryotes). This feature distinguishes them from protozoa which have a more complex cellular structure and a distinct nucleus (eukaryotes). Not all bacteria cause diseases. Bacteria are present in some fermented foods. Yogurt, for example, has Lactobacillus bulgaricus and Streptococcus thermophilus bacteria. The human mouth and intestines harbor over 400 different types of bacteria that produce some vitamins and ferment fiber to produce short-chain fatty acids. Bacteria that cause diseases are called "pathogenic" bacteria. Antibiotics, like penicillin, are substances that are toxic to the bacteria, but relatively harmless to people. They have been very useful in combating disease, but their increased use has produced antibiotic-resistant bacteria. Bacteria are classified by their shape and the color that they take when stained. A bacillus is elongated like a sausage, a coccus is round, and a spirochete is helical (spiral) in shape. Hans Christian Gram (1853-1938) developed a staining technique that colors some bacteria deep blue (Gram positive), whereas others take on a red color (Gram negative). Here is a list of common bacteria and some of their attributes:

• Staphylococcus - normally found on the skin, but can cause boils and pimples.
  Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for many
  serious infections that are sometimes fatal.
• Escherichia coli - normal inhabitant of the colon, hence called "coliform" bacteria
  E. coli O157:H7 is a virulent strain that produces toxins that
  can cause diarrhea, abdominal pain, and even kidney failure.
• Chlamydia - a sexually transmitted disease (STD) caused by the bacterium Chlamydia trachomatis.
  Over one million cases of chlamydia were reported in the United States in 2006.
  Learn more about sexually transmitted diseases.
• Salmonella - frequent cause of food poisoning
• Vibrio cholerae - causes cholera, an infection of the small intestine characterized by watery diarrhea
• Treponema pallidum - a spiral-shaped (spirochete) bacteria that causes syphilis
• Neisseria gonorrhoeae - a Gram-negative coccus that causes gonorrhea, one of the most common sexually transmitted diseases
• Borrelia - a spirochete transmitted by ticks that causes Lyme disease (borreliosis).
• Mycobacterium tuberculosis - the cause of tuberculosis
• Yersinia pestis - causes bubonic plague, transferred by flea bites
• Bacillus anthracis - the organism that causes anthrax, characterized by black lesions.
• Rickettsia - a motile, Gram-negative bacterium that replicates only within the cytoplasm of cells and causes diseases such as typhus, rickettsialpox, and Rocky Mountain spotted fever. It is transmitted by the bites of insects such as ticks, fleas, and lice.

Parasites
Parasites may be protozoa, fungi, or multi-cellular organisms. Many parasites have complex life cycles that insure their proliferation and survival.

Protozoa
As mentioned above, protozoa have a more complex organization than bacteria. Some protozoa form cysts that protect them from harsh conditions and enable them to live outside of a host for a long time. Some diseases caused by protozoans are:

• Malaria (transmitted by mosquitos) is most prevalent in Sub-Saharan Africa
• Leishmaniasis (transmitted by sandflies which are about one-third the size of mosquitoes)
• African trypanosomiasis (sleeping sickness transmitted by the tsetse fly)
• Amoebic dysentery - infection of the intestine caused by an ameba (Entamoeba histolytica), which causes severe diarrhea.
• Coccidiosis - intestinal infection that causes bloody diarrhea.
• Cryptosporidiosis - parasitic disease of the intestine caused by Cryptosporidium.
• Giardial enteritis - an infection of the small intestine caused by Giardia lamblia.
• Toxoplasmosis - a systemic parasitic infection transmitted by eating undercooked meat or contamination by cat feces.

Malaria, a debilitating disease that causes high fevers, is contracted through the bite of an infected mosquito. The parasite reproduces within the human liver and red blood cells (shown above), and it is transmitted back to other mosquitos when they feed on the infected person. Mosquitoes and flies are also vectors of parasitic diseases such as sleeping sickness and elephantiasis.

Fungi
Fungi include one-celled yeasts slightly bigger than bacteria, and multi-celled mushrooms and molds. Fungi do not have chlorophyll to make their own food, so they get their nutrition as parasites or by breaking down remains of dead plants or animals. Some fungi are poisonous (e.g., Amanita mushrooms), but some have beneficial uses. For example, Penicillium notatum produces the antibiotic penicillin and Saccharomyces cerevisiae is the yeast used to make bread rise and to brew beer. Fungal diseases are called mycoses and include:

• Aspergillosis - infection of sinuses and lungs
• Blastomycosis - skin and pulmonary infections
• Candidiasis - cutaneous and vaginal infections. Candida albicans is the most common cause of vaginal yeast infections.
• Coccidioidomycosis - may cause cough, chest pain, shortness of breath
• Cryptococcosis - may be transmitted in pigeon droppings
• Histoplasmosis - an infection caused by breathing in spores of a fungus often found in bird and bat droppings.

Some fungal infections are more common in certain geographic areas.

Blastomycosis is caused by a fungus (Blastomyces dermatitidis) typically found in decomposing organic material like mulch. The fungus is common in the Great Lakes area of the Upper Midwest and the southeastern and south central regions of the United States. The spores are released into the air when soil is disturbed by farming, construction or wind.

Coccidioidomycosis, also known as valley fever, is caused by fungi (Coccidioides immitis or Coccidioides posadasii) found in the desert soils of the Southwest, most notably in California and Arizona. These fungi also can be released into the air by wind or road traffic that disrupts the soil.

Histoplasmosis is a lung infection caused by the fungus Histoplasma capsulatum, which is commonly found in the Midwest along the valleys of the Mississippi, Missouri and Ohio rivers. Fungal spores may also occur in bird and bat droppings found in farms, abandoned buildings, caves and bird roosts.

Recommended prevention measures can include use of gloves, facemasks and respirators for persons engaged in agriculture, construction and other activities that generate dust or require handling soil.

Multicellular parasites
Multicellular parasites include various kinds of worms and fungi that cause diseases such as:

• Ascariasis (roundworms)
• Hookworm
• Lymphatic filariasis or elephantiasis (transmitted by mosquitos)
• Pinworm
• Schistosomiasis (liver or blood flukes)
• Tapeworm
• Trichinosis - a disease caused by consumption of poorly cooked meat that contains cysts of Trichinella spiralis.
• Tinea corporis, tinea pedis (ringworm, athlete's foot)

Intestinal parasites are commonly transmitted by eating food contaminated with feces or by eating raw or undercooked meat and seafood. In many parts of the world, manure or feces are used for fertilizing crops, and this is how vegetables and drinking water can become contaminated with the eggs or larvae of parasitic organisms. It is estimated that the human pinworm affects approximately 50% of the children in the United States. Pinworms lay their eggs around the anus and cause itching. The natural instinct to scratch, in combination with habits like thumb sucking and poor hand-washing, spreads the parasites. Tapeworms and roundworms can infect the body when their eggs or larvae are swallowed by eating raw or undercooked meats (pork) or seafood (ceviche, salmon roe, sashimi, sushi, cold-smoked fish). Protozoan parasites are frequently present in raw oysters.

Hookworms (Necator and Ancylostoma) are generally contracted by walking barefoot on soil contaminated by feces from infected animals or persons, or by swimming or wading in contaminated water. Hookworm larvae are capable of penetrating the skin in a few seconds. Once inside the body, they migrate to the lungs via the capillaries, and then cross into the air sacs of the lungs. They are eventually coughed up and swallowed. In the intestines, they feed on blood and reproduce. The females lay eggs that are passed in the feces to repeat the cycle.

Fungal Infections

Fungi and molds cause a variety of skin diseases such as athlete's foot, jock itch, and ringworm, but they can also cause pulmonary and internal infections such as aspergillosis, and candidiasis (yeast infection). The dermatophyte Trichophyton rubrum is a fungus that frequently causes chronic infections of the skin and nails. Tinea capitis is a fungal infection of the scalp that causes severe itching, dandruff, and bald patches. Tinea corporis, commonly known as ringworm, is an infection of the skin found on the body, such as the trunk and limbs. Tinea pedis is a superficial fungal infection affecting the feet, often called athlete's foot. This type of fungal infection typically is found in the skin between the toes, and is characterized by itching, blisters, cracking, and scaling. Tinea cruris, also known as jock itch, is a fungal infection of the skin of the groin area. Fungal infections are aggravated by sweating, restrictive garments, not washing and drying the body carefully on a daily basis, and by not changing into clean clothing frequently enough.

Ringworm and other fungus skin infections can be treated with a variety of non-prescription antifungal ointments, powders, or sprays containing tolnaftate, clotrimazole, undecylenic acid, terbinafine hydrochloride, salicylic acid, etc.  White vinegar (5% acetic acid) is a common home remedy for fungal skin infections such as ringworm and athlete's foot; it is applied with a cotton ball in the morning and in the evening, but it produces a burning sensation on broken skin. To prevent re-infection, the fungi that cause skin infections should be eliminated from environmental surfaces like bathtubs and toilet seats by washing the surfaces with diluted household chlorine bleach, which is a solution containing typically 5.25% sodium hypochlorite (NaOCl). Fungi on towels, sheets, socks, underwear, and other clothing can also be killed by adding bleach during the wash cycle, although this may fade some fabrics. In the case of athlete's foot, shoes should also be treated with antifungal foot powder. For tinea capitis infections, pillows, pillow cases, combs, hats, and hair brushes must be disinfected. Chlorine bleach should not be used on the skin because it is extremely caustic and will cause chemical burns. Wear rubber gloves when handling bleach.

Fungal nail infections are difficult to cure because the fungi infect the nail bed and topical medicines cannot penetrate through the keratin of the nails. In severe cases, a doctor might remove the nail completely before applying a topical medicine. Often, doctors prescribe antifungal pills taken by mouth that can take several months to a year to cure the infection. The cost of oral treatments ranges from about $250 to $500, and there are many serious side effects. An effective and economical remedy for nail fungus consists of applying one drop of iodine tincture daily to the tip of the affected toenail for several weeks (Davidson, 2006).