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Infectious diseases affect people worldwide. Symptoms range from mild to severe, and treatment depends on the cause of the illness.
Infectious diseases can be caused by many pathogens, including bacteria, viruses, fungi, and parasites that may cause illness and disease. For humans, transmission of pathogens may occur in a variety of ways: spread from person-to-person by direct contact, water or foodborne illness or aerosolization of infected particles in the environment and through insects (mosquitoes) and ticks. Signs and symptoms and treatment of infectious diseases depend on the host and the pathogen. Who is most at risk for getting infectious diseases?Anyone can get an infectious disease. People with a compromised immune system (an immune system that doesn’t work at full strength) have greater risk for certain types of infections. Those at higher risk include:
How common are infectious diseases?Infectious diseases are extremely common worldwide. Some infectious diseases strike more often than others. For instance, in the United States, 1 out of every 5 people is infected with the influenza (flu) virus each year. What complications are associated with infectious diseases?Many infectious diseases cause complications. These can range from mild to severe. For some conditions, complications may include wheezing, skin rash, or extreme fatigue. Mild complications usually disappear as the infection resolves. Certain infectious diseases may cause cancer. These include hepatitis B and C (liver cancer), and human papillomavirus (HPV) (cervical cancer).
Symptoms of infectious disease are particular to the type of disease. For example, symptoms of influenza include:
Other infectious diseases, such as Shigella, cause more serious symptoms, including:
You may experience one or several symptoms of an infectious disease. It’s important to see a doctor if you have any chronic (ongoing) symptoms or symptoms that get worse over time. What causes infectious diseases?Infectious diseases in humans are caused by microorganisms including:
Infectious diseases spread in multiple ways. In many cases, direct contact with a sick individual, either by skin-to-skin contact (including sexual contact) or by touching something another person touches, transmits the disease into a new host. Contact with body fluids, such as blood and saliva, also spreads infectious diseases. Some diseases spread through droplets discharged from a sick person’s body when they cough or sneeze. These droplets linger in the air for a short period of time, landing on a healthy person’s skin or inhaled into their lungs. In some cases, infectious diseases travel through the air for long periods of time in small particles. Healthy people inhale these particles and later become sick. Only certain diseases spread with airborne transmission, including tuberculosis and the rubella virus.
Doctors diagnose infectious diseases using a variety of laboratory tests. Samples of blood, urine, stool, mucus or other body fluids are examined and provide information used in the diagnostic process. In some cases, doctors identify infectious organisms by examining them under a microscope. Occasionally, laboratories must grow, or culture, the infectious organism from a sample to confirm its presence.
Treatment depends on which microorganism causes the infection.
In all cases, doctors treat specific symptoms of infectious diseases according to the latest medical guidelines. Talk with your doctor about your symptoms to explore possible treatment options.
Vaccines are available to prevent many common infectious diseases, including hepatitis, diphtheria, influenza and herpes zoster. The CDC has updated recommendations for vaccinations for children, adolescents and adults. There are new platforms for delivery of vaccinations and research on new pathogens. It is also important to consult with a travel clinic prior to travel overseas to be sure you are protected. You can also reduce your risk of contracting an infectious disease by:
With treatment, most people recover fully from infectious diseases. Some infectious diseases, like HIV (human immunodeficiency virus), cannot be cured yet. Instead, doctors focus on symptom management and preventing the disease from progressing further. Increasingly, antibiotic medications may not be effective against certain infectious diseases. Gonorrhea, a sexually transmitted infection affecting both men and women, is usually treated with antibiotics. Recently, doctors have identified drug-resistant strains of the bacteria that causes gonorrhea. These resistant strains are much less likely to respond to treatment with antibiotics. It’s important to seek care from a doctor who can help you find the right therapy for a persistent infection.
Let your doctor know if you have any symptoms of an infectious disease, especially if they are unusual or don’t go away over time. Symptoms like fever, vomiting and diarrhea may lead to more serious complications, including dehydration. Your doctor should also know if you plan to travel to foreign countries. You may need to be vaccinated against common infectious diseases occurring at your destination. If you have an ongoing infection, frequent follow-ups with your doctor help ensure your condition does not worsen.
Last reviewed by a Cleveland Clinic medical professional on 02/27/2018. References
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