Infectious diseases are disorders caused by organisms — such as bacteria, viruses, fungi or parasites. Many organisms live in and on our bodies. They’re normally harmless or even helpful, but some organisms under certain conditions may cause disease.
Some infectious diseases can be passed from person to person. Some, however, are transmitted via bites from insects or animals. Others are acquired by ingesting contaminated food or water or other exposures in the environment.
Signs and symptoms vary, but often include fever and chills. Mild complaints may respond to home remedies, while some life-threatening infections may require hospitalization.
Many infectious diseases, such as measles and chickenpox, can be prevented by vaccines. Frequent and thorough hand-washing also helps protect you from infectious diseases.
Each infectious disease has its own specific signs and symptoms. General signs and symptoms common to many infectious diseases include:
Loss of appetite
When to see a doctor
You should seek medical attention if you:
Have been bitten by an animal
Are having trouble breathing
Have been coughing for more than a week
Have severe headache with fever or seizures with fever
Experience a rash or swelling
Have unexplained fever
Infectious diseases can be caused by:
Bacteria. These one-cell organisms are responsible for illnesses such as strep throat, urinary tract infections and tuberculosis.
Viruses. Even smaller than bacteria, viruses cause a multitude of diseases — ranging from the common cold to AIDS.
Fungi. Many skin diseases, such as ringworm and athlete’s foot, are caused by fungi. Other types of fungi can infect your lungs or nervous system.
Parasites. Malaria is caused by a tiny parasite that is transmitted by a mosquito bite. Other parasites may be transmitted to humans from animal feces.
Most infectious diseases have only minor complications, but some infections — such as pneumonia, AIDS or meningitis — can become life-threatening. A few types of infections have been linked to a long-term increased risk of cancer:
Human papillomavirus is linked to cervical cancer
Hepatitis B and C increase the risk of liver cancer
Helicobacter pylori is linked to stomach cancer
Knowing what type of germ is causing your illness makes it easier for your doctor to choose appropriate treatment.
Antibiotics are grouped into “families” of similar types. Bacteria also are put together in groups of similar types, such as streptococcus or E. coli. Certain types of bacteria are especially susceptible to particular classes of antibiotics. So treatment can be targeted more precisely if your doctor knows what type of bacteria you’re fighting.
Antibiotics are reserved for bacterial infections, because these types of drugs have no effect on illnesses caused by viruses. But sometimes it’s difficult to tell which type of germ is at work. For example, some types of pneumonia are caused by viruses while others are caused by bacteria.
The overuse of antibiotics has resulted in several types of bacteria developing resistance to one or more varieties of antibiotics. This makes these bacteria much more difficult to treat.
Drugs have been developed to treat some, but not all, viruses. Examples include the viruses that cause:
Severe fungal infections can affect the lungs or the mucous membranes of the mouth and throat — most commonly in people who have weakened immune systems. Antifungals are the drugs of choice for these types of infections.
Some diseases, including malaria, are caused by tiny parasites. While there are drugs to treat these diseases, some varieties of parasites have developed resistance to the drugs.
Infectious agents can enter your body through:
Skin contact or injuries
Inhalation of airborne germs
Ingestion of contaminated food or water
Tick or mosquito bites
Follow these tips to decrease your risk of infecting yourself or others:
Wash your hands. This is especially important before and after preparing food, before eating and after using the toilet.
Get vaccinated. Immunization can drastically reduce your chances of contracting many diseases. Make sure to keep your recommended vaccinations, as well as your children’s, up to date.
Stay home. Don’t go to work if you’re vomiting, have diarrhea or are running a fever. Don’t send your child to school if he or she has these signs and symptoms, either.
Prepare food safely. Keep counters and other kitchen surfaces clean when preparing meals. In addition, promptly refrigerate leftovers — don’t let cooked foods remain at room temperature for extended periods of time.
Practice safe sex. Use condoms if you or your partner has a history of sexually transmitted infections or high-risk behavior.
Don’t share personal items. Use your own toothbrush, comb and razor. Avoid sharing drinking glasses or dining utensils.
Travel wisely. Don’t fly when you’re ill. With so many people confined to a small area, you may infect other passengers on the plane. And your trip won’t be comfortable, either. If you’re traveling out of the country, talk to your doctor about any special vaccinations you may need.