Germs: The Silent Killers

My name is Jennifer and I am obsessed with science. I am currently a high school senior, and I'm in AP Bio and AP Chem. This blog is dedicated to my interest in germs: bacteria, viruses, parasites, and fungi. I hope to teach some of you about diseases:...

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HIV and AIDS

AIDS (acquired immunodeficiency syndrome) is talked a lot about in the media, but not everyone knows what it is and how to protect themselves from getting it.

Someone cannot immediately get AIDS; they must first contract HIV (human immunodeficiency virus). HIV can be spread through: unprotected sex, the use of contaminated needles (due to sharing drug needles or an accidental puncture at a hospital), mother-to-child transmission (25-33% of women with HIV pass it on to their children during vaginal birth), and unsafe blood transfusions (now all hospitals in the US are required to screen for HIV in the blood and if it is detected the blood will undergo heat treatment to get rid of the virus before transfusion). In order to reduce the risk of spreading HIV: use condoms during intercourse (it is the only contraceptive that protects against STDs), don’t share needles, and mothers will take drug treatment to protect their baby from contracting it during vaginal birth or she will elect to have a Cesarean section (which reduces the probability of infection to 1%).

Once someone gets HIV, the virus could remain dormant in their body for years or it could immediately start multiplying and destroying immune system cells. HIV slowly disables/kills T cells often without causing severe symptoms. As a result, the immune system is drastically compromised and symptoms will result, for example: enlarged lymph nodes, fatigue, weight loss, fever, sweats, persistent fungal/viral infections, short-term memory loss, and stunted growth in children.

After years of having HIV, the patient’s T cell count dips below 200 CD4+ T cells per cubic mm of blood (the healthy amount is 1,000 or more) and they now officially have AIDS. Possible symptoms are: coughing, shortness of breath, weight loss, headache, and lack of coordination. Just like with HIV, AIDS also increases the risk of the patient contracting opportunistic infections, but since the immune system is so much weaker now, patients are more likely to die from them. 

Neither HIV nor AIDS can be cured because the disease is caused by a virus. The only way to combat them is to take doctor prescribed drugs that inhibit viral reproduction which only delay the effects of the disease, so the best way to protect yourself is to take caution to not contract the virus in the first place because HIV and AIDS are life-threatening.

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Fungal Infections

Fungal infections (aka mycoses), however mild they seem, are extremely prevalent. In 2010, it was the 4th most common type of infection in the world, affecting over 950 million in that year. This may be due to the vast amount of fungi in the environment. There are about 300 species of fungi that are pathogenic (can make us sick). Although we usually think of fungal infections as diseases on the skin, it may originate in the: skin, hair, nails, or lungs and then spread to any organ or organ system and cause serious damage.

People with low immune systems or those who are currently taking antibiotics or have recently stopped taking antibiotics are at a higher risk of contracting a fungal infection. Antibiotics increase risk because there are good bacteria that can fight off fungal spores to prevent fungal reproduction in your body, but if the good bacteria are killed by the antibiotics then your body is less defended against these pathogens. Being barefoot or having a break in the skin in a damp/wet environment such as a public shower also increases risk of infection(ex: athlete’s foot).

Most mycoses are diagnosed visually, but some require scrapings (nail infections), a throat swab, or UV light for a diagnosis. For treatment, a patient may be prescribed: antifungal cream, drops, ointment, or in serious cases- oral tablets or injections. 

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Food Poisoning

Food poisoning is one of the most common illnesses worldwide. It usually arises from contamination of raw meat (sushi or undercooked meat). Food may be contaminated by bacteria, viruses, parasites, and toxins. Food poisoning can be caused by more than 200 diseases that lead to gastrointestinal (GI) upsets of varying severity. The symptoms that may result from food poisoning are: upset stomach, nausea, vomiting, diarrhea, and fever. In severe cases, it may cause dehydration and death. It can be diagnosed by a blood or stool test. In the United States, about 76 million people get food poisoning every year, 325,000 are hospitalized, and 5,000 die. In most cases, treatment is rest and fluids, but in severe cases an IV may be prescribed at a hospital to rehydrate the patient. Antibiotics may be used to treat food poisoning if the disease is of bacterial origin.

These food poisoning-causing microorganisms may produce toxins before or after ingestion. If toxins are produced before ingestion then it is not communicable. If they are produced after ingestion then it may spread from person to person.

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Parasites

Parasites can be unicellular organisms or multicellular animals. There are two main types of parasites that are important in regards to humans. Ectoparasites live outside the body, usually on the host’s skin (ex: ticks, lice, leeches). Endoparasites live inside of their host (ex: tapeworms, roundworms). Some endoparasites require a vector to transmit them to the host (ex: Plasmodium protozoan is transmitted to its host through the help of the female Anopheles mosquitos while it is sucking the animal’s blood).

Parasites are usually harmful to their host, and they are most common in rural parts of: Africa, Asia, Latin America, and the US.

A diagnosis may be made for the type of parasite through blood tests, x-rays, CAT scans, MRIs, endoscopy/colonoscopy, and/or by testing for blood in stool, urine, or infected tissue.

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Cholera and Measles: Diseases of the Past?

When we think about diseases such as cholera and the measles, we think about how horrible they were in the past because they are long gone, but that is only half true. They were horrible diseases, but they are still apparent in society today. Re-emergent diseases like these are popping back up in society today, because we as humans are changing their environment through: changes in agriculture, increased population density of humans and vectors (disease carriers such as rats or mosquitos), decreased health standards, etc.

The cholera bacterium re-emerged in the 1990’s after South American governments reduced the level of chlorine they were using to treat the water supplies.

In addition, the incidence of the measles virus in the U.S. population increased after budget cuts to the immunization programs.

So if we want to reduce the resurgence of terrible diseases, we shouldn’t be trying to modify the behavior of germs so much as we should our own behavior.

Source: Emerging Viruses by Stephen S. Morse

Additional Readings:

http://wwwnc.cdc.gov/eid/article/4/3/98-0326_article

http://www.nytimes.com/1992/01/19/weekinreview/a-resurgence-of-plagues-and-pestilences-of-yesteryear.html

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Image above: E. coli bacteria

How Do Pathogenic (disease-causing) Bacteria Work?

Pathogenic bacteria can get inside your body in a number of ways. For example, they can get in: through a cut, a mucous membrane, by you eating, or even by you breathing. Thousands of bacteria and viruses enter your body every day just by inhaling, but most of these are non-harmful or are killed by your immune system before you notice. Once bacteria get inside you, they absorb nutrients from the food you digested, and as a waste product, bacteria excrete toxins, which are poisonous to your body and interfere with your cellular functions. Bacteria reproduce asexually, so if even one bacteria gets in an organism, it can create a colony large enough to do some serious damage with all the toxins that are produced. This triggers your immune system and either you can fight off the infection by yourself or you have to go to the doctor to get medicine.

The doctor’s office will prescribe antibiotics, which are supposed to kill the harmful bacteria in your body. This however, isn’t always the case. All living things are constantly evolving and unfortunately bacteria are evolving to be resistant to antibiotics due to incorrect use, so if you get for example strep throat and are prescribed penicillin or amoxicillin, the medicine may not work against this superbug (strains of bacteria that are resistant to several types of antibiotics). In this case, unfortunately, you may have to just tough it out.

Sources:

http://www.microbeworld.org/types-of-microbes/bacteria

http://www.wisegeek.com/what-are-bacterial-toxins.htm

The Encyclopedia of Infectious Diseases, 3rd Edition by Carol Turkington and Bonnie Lee Ashby, M.D.

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What Are Bacteria?

Bacteria are unicellular organisms that vary in: size, shape, method for ascertaining nutrients, whether or not they require oxygen, and whether or not they can move. When we think about bacteria, we usually imagine getting sick, but only 1% of all bacteria can make us ill. Most bacteria are non-harmful to us and are helpful to the environment by: assisting in decomposing dead organisms, fixing nitrogen in the soil so it is usable by plants, and breaking down food in animals’ digestive systems. In fact, there are over 400 different types of bacteria in our stomach right now helping us to get nutrients from our food. Without these helpful bacteria, harmful bacteria could colonize the digestive system easier and we would be sick a lot more often. So next time you hear the word bacteria, think about what life would be like without it (hint- life wouldn’t exist!).

Sources:

http://www.microbeworld.org/types-of-microbes/bacteria

http://www.wisegeek.com/what-are-bacterial-toxins.htm

The Encyclopedia of Infectious Diseases, 3rd Edition by Carol Turkington and Bonnie Lee Ashby, M.D.

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It’s important to learn exactly what a fungus is to know how fungi can be both beneficial and detrimental to our bodies. This video does a good job of going over the basics.

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Hank Green talks about parasites on the Sci Show.

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Fun Facts About Germs

Did you know….?

tapeworms (a type of parasite) don’t have their own digestive systems, they just absorb all their nutrients from their skin (Ew!)

when you get a parasite, that might not be the only thing you have to worry about. Parasites may be infected by bacteria or viruses of their own and transfer it to you (ex: mosquitoes are vectors for malaria)

fungi secrete enzymes that break down food outside of their bodies and then absorb the nutrients, because they do not have stomachs to digest complex molecules 

the mushrooms that we see outside are examples of harmless decomposers, other fungi live in mutualistic (good for both organisms) relationships, but some fungi use living organisms for food which causes diseases (ex: athlete’s foot and ringworm)

there are 10 times as many bacterial cells in your body as human cells

there are more than 500 species of bacteria in human intestines

although viruses have DNA and RNA, they are not considered alive, because they are obligate parasites (require a host to reproduce)

viruses are so much smaller than bacteria that they are even smaller than bacterial ribosomes 

Sources:

http://www.encyclopedia.com/topic/Parasites.aspx

http://herbarium.usu.edu/fungi/funfacts/kingfact.htm

http://www.scientificamerican.com/article/strange-but-true-humans-carry-more-bacterial-cells-than-human-ones/

http://www.encyclopedia.com/topic/virus.aspx

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How Do We Protect Ourselves From Viruses?: The Third Line of Defense

The third line of defense includes macrophages that may recognize the antigens (protrusions for attaching to cells) on viruses and engulf the virus to present it to T cells with a complimentary receptor. These T cells then multiply and differentiate into: killer T cells, helper T cells, suppressor T cells, and memory T cells. Killer T cells attach directly to the viral antigens and destroy the virus immediately. Helper T cells help B cells produce antibodies, activate macrophages, and stimulate inflammation. Suppressor T cells turn off the immune response when the virus is gone from the organism, and memory T cells remain in the body for up to 10 years to be ready to combat the virus if there is a reinfection. Antibodies, which are produced by helper T cells and plasma B cells, also have an important function, because they bind to the viral antigens and “tag” the virus so the phagocytes know what to attack. If the virus manages to evade the first, second, and third lines of defense, symptoms will worsen and medication will be required to overcome the illness.

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Why Should You Care If Plants and Animals Get Sick?

Whether or not you sympathize with infected plants or animals, you should care because it could directly affect you. Studies show that bacteria and viruses can broaden their host specificity (what species they can infect). Bacteria have evolved to live in many different types of environments and they can alter their environment by secreting chemicals that make it easier to live in. Viruses have a high mutation rate which allows for the viruses with mutated genes to permeate the defenses of different species.

The pepper mild mottle virus, which was originally found only in plants, has been shown to cause symptoms such as: abdominal pain, damage to the colon, and fever in humans who have traces of the virus in their feces.

Another more well known example of host variation would be the Ebola virus being transferred from monkeys in Africa to hunters. This is a much more deadly example than the pepper mild mottle virus, since Ebola causes excessive bleeding from the mucus membranes and eventually causes death.

These examples illustrate that a disease a plant or animal has may affect us, so regardless of your feelings towards them, scientists and the government should strive to learn more about how these pathogens adapt and mutate so we can prevent humans from getting these emerging diseases.

Sources:

https://lifescienceexplore.wordpress.com/2014/08/16/bacteria-can-colonize-new-hosts-by-modifying-their-environment/

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC98959/

http://www.virology.ws/2010/04/29/can-a-plant-virus-make-you-sick/

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Epstein-Barr Virus (EBV)

Epstein-Barr Virus (EBV) is the cause of infectious mononucleosis (aka mono), and it is in the herpes family. This disease is particularly harmful because it can also cause cancer of the head and neck and it increases one's likelihood of getting autoimmune diseases such as HIV, multiple sclerosis, and rheumatoid arthritis. And since EBV attacks epithelial cells lining the throat, short-term flu-like symptoms associated with mono such as fatigue, sore throat, fever, abdominal pain, sore muscles and headache as well as the long-term conditions associated with EBV may develop. The Epstein-Barr Virus may be transmitted through the exchange of saliva and/or genital secretions, but even though mono is called the kissing disease, it can be spread by sharing a drink or food as well. This is why 50% of children in the US and England test positive for EBV at age 5, and 90% of adults 35-40 have been infected at one point in their lives. The primary target for EBV is college students, so be careful out there. Unfortunately, EBV does not have a vaccine, so the best prevention is keeping food and drink to oneself. Fortunately, most often symptoms disappear on their own. If symptoms persist, a doctor visit is required.

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Who is More Likely To Get Sick?

There are several factors that affect whether or not someone will get sick. The main factor, however, is their immunity. If someone has never been exposed to a disease before, then they are more likely to get infected than someone who has been invaded by that pathogen (anything that can cause disease- aka a germ), because the person who has been infected before will have memory B cells stored up in their body waiting for that same germ to attack. If that person has memory B cells for that pathogen already, then their immune system can quickly identify and mount an attack on the foreign invader. The people who don’t have memory B cells specific to that microbe will take longer to recognize an invader and fight it off and may get sick, which is a result of the immune system having to work harder to combat the microbe (ex: trying to burn out the microbe causes fever). Immunity can also be decreased by diseases such as AIDS (auto-immune deficiency disorder), a change in diet, or if someone is a young child or an elderly person.

The most important things you can do to prevent from getting sick would be to: eat healthy, get enough sleep, wash your hands and body frequently, and to get vaccinated for everything the CDC or your doctor recommends for you or someone in your area.

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What is Malaria?

Malaria is a disease caused by a single-celled parasite in the Plasmodium genus. There are over 150 different species of the “malaria parasite” that can infect vertebrates. Luckily, there are only four types that can infect humans. It is transmitted through the female Anopheles mosquito (because the males don’t drink blood). Mosquitoes have two tubes that they stick into their prey, one tube is for depositing anticoagulants to keep blood flowing to make it easier for them to drink the blood and the other tube is for sucking up the blood. Unfortunately, if the mosquito is infected with a Plasmodium parasite, the parasite is also injected into the animal along with the anticoagulants. Once the parasite gets into the blood it begins feeding on the animal’s erythrocytes (red blood cells aka RBCs) and reproduces within the erythrocytes. For the next generation to exit the erythrocytes, the parasites burst out, which kills the animal RBCs. This causes all kinds of symptoms such as: fever, chills, headaches, nausea, vomiting, diarrhea, shaking, jaundice (the yellowing of the skin and eyes), and enlarged liver & spleen. Every year there are between 300 million and 500 million cases worldwide and of those infected, between 1 million and 3 million people die. Treatment and prevention are usually too expensive for the underdeveloped countries where most cases occur in, but when it is possible prevention such as mosquito nets and treatments such as anti-malarial pills can help reduce the amount of deaths. Mosquitoes have increasingly become resistant to insecticides, however, as well as the malarial parasite has become more resistant to anti-malarial drugs. As there is not yet a vaccine or cure for malaria, there is an ongoing battle against the disease.

Source:

Diseases and Disorders by Marshall Cavendish Corporation

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Flu Attack! How a Virus Invades Your Body- by NPR