While the words "infectious" and "contagious" are often used interchangeably to describe illnesses, they actually mean two very different things.

Infectious Disease

Put simply, an infectious disease is an infection. That is, when a microorganism comes into your body, and makes itself comfortable. For bacteria or fungi, this means dividing and growing new cells at an exponential rate. Viruses, on the other hand, have an added hurdle of entering human cells and taking over their control centers so that they can make more of themselves.

Infectious & Not Communicable

While all communicable diseases are infectious, not all infections are communicable. Tetanus, for example, can cause an infection, but a person with tetanus can't spread it to other people.1 The bacteria live in dirt and dust and get inside your body through abrasions like cuts, scrapes, or punctures. While the pathogen can lead to a very serious infection and illness in individuals, it will almost certainly never cause a worldwide pandemic.

Invisible Infections

The human papillomavirus is an example of a pathogen that can cause infection but not necessarily symptoms. Nearly all adults in the United States will get infected with HPV, but most don't even realize it.2While the virus can lead to genital warts or cancer in some people, the vast majority of the time it doesn't cause any symptoms at all. Your body is able to clear the infection without you ever getting sick

Communicable Disease

A communicable disease is a contagious one. The effect is external. If someone catches the illness, they can get sick and spread the pathogen—be it a cold, virus, or some other disease-causing agent—onto the next person. This can lead to small, isolated outbreaks or full-scale pandemics. An example of this happens each and every year in the United States from roughly October to May: the flu. As influenza viruses are passed from person to person and via contaminated objects, the virus spreads far and wide. For every one person with the flu, another one to two others will likely become infected if they aren't immune. This rate of how fast a pathogen can spread is called the basic reproductive number, or R0, and it depends on a wide variety of factors, including how the microbe travels to new people

You can consult a family medicine practitioner or an internist, as to take more examinations for your health or another serious condition that also requires medical attention.