Infectious diseases occur when a type of microorganism impairs a person’s health. In many cases, infectious disease can be spread from person to person, either directly (e.g., via skin contact) or indirectly (e.g., via contaminated food or water).

Infectious diseases can be caused by organisms such as viruses, bacteria, fungi or parasites. Most of these are already in our bodies and generally harmless, sometimes even helpful but under certain conditions they may cause diseases. These diseases could be mild and treatable with home remedies and rest, but in some cases these can be life-threatening.

Examples of conditions that are commonly evaluated and treated by an infectious disease specialist are:

  • Infections of the Skin (Cellulitis)
  • Soft tissue and bone infections (Osteomylitis)
  • Recurrent infections – pneumonias, sinusitis, or urinary tract infections
  • Staph infection (MRSA)
  • Diabetic foot infection
  • Infectious diarrhea and other parasitic intestinal infections
  • Post-surgical infections
  • Fever of unknown cause
  • Travel medicine and illnesses related to travel to developing countries

Who is most at risk for getting infectious diseases?

Anyone can get an infectious disease. People with a compromised immune system have greater risk for certain types of infections.

Those at higher risk include:

  • People with suppressed immune systems, undergoing cancer treatment or those who have recently had an organ transplant
  • Individuals who are unvaccinated against common infectious diseases
  • Healthcare workers
  • People travelling to high-risk areas where they may be exposed to mosquitoes that carry pathogens such as malaria, dengue virus and Zika viruses.


While fever and fatigue are among the most common symptoms, all signs and symptoms vary depending on the organism causing the infection. Each infectious disease has its own specific signs and symptoms.

General signs and symptoms common to a number of infectious diseases include:

  • Fever
  • Diarrhea
  • Fatigue
  • Muscle aches
  • Coughing


Direct contact

Some infectious diseases can spread when you come directly into contact with a person who has an infection, via touching, kissing or having sex. Direct contact with the bodily fluids of a person who has an infection can also spread infections in some instances. These include:

  • blood
  • nasal secretions
  • saliva
  • semen
  • vaginal secretions

Some infections can also be spread directly from an infected mother to her child either through the placenta or during childbirth, and even through breast milk.

Indirect contact

Some infectious organisms are found in your environment. Coming into contact with these can spread the infection. A common example of this is when someone with the flu coughs or sneezes, the influenza virus can then be present in the air or on objects such as door and faucet handles. If you touch any of these contaminated objects and then touch your face, mouth or nose, there is a high probability of you getting infected.

Through contaminated food or water

In some cases, food or water may be contaminated with infectious organisms. You can get these infectious diseases by consuming things like:

  • foods prepped or prepared in unsanitary conditions
  • raw or undercooked foods, such as produce, meats or seafood
  • improperly canned foods
  • unpasteurized milks or juices
  • foods that have been improperly stored or refrigerated

From an infected animal

Infectious diseases can also spread to people from an infected animal. For example the rabies virus, which you can get if an infected animal bites you. Another example is toxoplasmosis. You can come down with this parasitic disease from changing an infected cat’s litter box.

From a bug bite

There are many different types of biting bugs, including ticks, mosquitoes and lice. In some cases, you can get an infection if a bug carrying around an infectious microorganism bites you. Some examples include malaria, Lyme disease and West Nile Virus.


Here are some tips to reduce the risk of infection.

Wash your hands. This is especially important before and after preparing food, before eating, and after using the toilet. Avoid touching your eyes, nose or mouth with your hands, as that's a common way germs enter the body.

Get vaccinated. Vaccination can drastically reduce your chances of contracting many diseases. Make sure to keep up to date on your recommended vaccinations, as well as your children's.

Stay home when ill. Don't go to work if you are vomiting, have diarrhea or have a fever. Don't send your child to school if he or she has these signs, either.

Prepare food safely. Keep counters and other kitchen surfaces clean when preparing meals. Cook foods to the proper temperature, using a food thermometer to check for doneness. Also promptly refrigerate leftovers — don't let cooked foods remain at room temperature for long periods of time.

Practice safe sex. Always use condoms if you or your partner have 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. If you're travelling out of the country, talk to your doctor about any special vaccinations you may need.