Communicable diseases, sometimes called infectious diseases, spread from creature to creature through a variety of methods, such as contact with bodily fluids or contaminated surfaces, insect bites, or airborne molecules. Viruses, bacteria, fungi, and parasites are the culprits behind these diseases.
There are many communicable diseases, ranging in severity from mild to life-threatening. Though most common communicable diseases are treatable or have vaccines, if one spreads rapidly through a population, it can lead to an epidemic or pandemic.
Arguably the most famous communicable disease is the common cold, a contagious infection of the sinuses, nose, throat, and windpipe. Over 200 types of viruses can cause a cold, but the most common is the rhinovirus.
The common cold usually spreads through contact with a surface or by breathing in moist air that contains the virus. For an infection to occur, the virus must then enter the mucous membranes, which are the moist linings in the mouth, eyes, and nose.
Ringworm is the general term for many conditions that feature one signature symptom: a ring-shaped rash. Some examples of ringworm infections include jock itch, athlete’s foot, and tinea corporis. Despite the name, ringworm is the result of a fungal infection, not a real worm. It can spread through interaction with a sick person or animal, as well as contact with contaminated surfaces like bathroom floors, towels, or soil.
Strep throat is a widespread infection of the throat and tonsils. During the course of the infection, the tonsils and surrounding area become inflamed, causing discomfort, sore throat, and coughing, among other symptoms. Strep throat draws its name from the bacteria responsible for the infection, group A.
Strep spreads similarly to other respiratory issues. However, the responsible bacteria can also grow in infected sores on the skin. Other people may develop an infection after touching these sores.
Influenza or the flu is another well-known communicable disease. This illness spreads through contaminated airborne droplets, surfaces, or person-to-person contact. Like cold viruses, flu viruses enter the body through the mucous membranes. Though the two conditions share similar symptoms, influenza is often more serious and can have life-threatening complications.
Escherichia coli, commonly shortened to E. coli, is a bacteria that lives in the intestines of healthy animals and people. Usually, the bacteria is harmless and helps the body digest food. However, some strains of E. coli can cause issues like stomach pain, diarrhea, and fever. These strains of E. coli make people sick by producing a toxin that damages the lining of the small intestine.
People develop E. coli infections by consuming contaminated food or water or touching the mouth with contaminated hands. Afterward, E. coli spreads between individuals when a person does not wash their hands after using the bathroom or touches fecal matter and then touches other people.
Every sexually transmitted infection (STI) is a communicable disease. Chlamydia is the most common STI globally. This infection spreads through sexual contact, including various forms of intercourse; interacting with a contaminated object; or through genital fluids. Chlamydia often has no symptoms but can cause pain, discharge, and itching.
Without treatment, chlamydia can lead to sexual dysfunction, drops in fertility, immune system problems, and organ damage.
Hepatitis is a viral infection involving inflammation of the liver. Usually, it begins as an acute infection, but it can become chronic. Five viruses cause hepatitis infections: hepatitis A to E. Each virus spreads slightly differently.
Hepatitis A and E spread through contaminated food and water. Hepatitis B is usually an STI but can spread from a pregnant mother to the fetus. Hepatitis C travels through contact with infected blood, often due to needle sharing. Hepatitis D only affects people with hepatitis B and has the same transmission methods as hepatitis B and C.
Human immunodeficiency virus (HIV) is a retrovirus that causes acquired immunodeficiency syndrome (AIDS). The virus destroys immune system cells, weakening the body against pathogens. HIV usually transmits during unprotected sex, but it may also travel through contaminated blood or from mother to infant during pregnancy, delivery, and breastfeeding.
AIDS is the final stage of HIV infection and usually occurs after 10 years without treatment. However, medicinal advances mean that today, not everyone with HIV develops AIDS.
An incredibly contagious infection, Ebola belongs to the viral hemorrhagic fever group of communicable diseases. These conditions damage the blood vessels, potentially leading to dangerous bleeding from the internal organs, ears, eyes, and mouth. The Ebola virus travels through contact with infected body fluids or objects containing these fluids. It is not airborne.
Historically, Ebola was fatal for as many as 90% of people, but that number is now closer to 50% due to advances in treatment and prevention methods.
Rabies is a communicable disease that causes serious symptoms like paralysis, hallucinations, and seizures. The condition spreads through direct contact with the saliva or nervous system tissue of an infected animal. Usually, this is due to the animal biting through a person or another animal's skin. Bats are the primary transmitters of rabies in the U.S.
Rabies is preventable with vaccination immediately following transmission but is fatal without treatment. The virus travels from the infection site through the nerves, damaging them severely. It can hide from the body’s immune system, allowing it to reach and destroy the brain.
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