Disease & Outbreaks

Terms to Know

Infectious Disease

It is a condition caused by the invasion and multiplication of harmful microorganisms in the body. These microorganisms, known as pathogens, can include bacteria, viruses, fungi, and parasites. Infectious diseases can spread through various means, such as contact with infected individuals, contaminated objects, or through vectors like insects.

Outbreak

It is when there's a higher-than-expected number of disease cases occurring within a specific time and location. It often requires further investigation to identify the source and mode of transmission. Outbreaks can be limited to a small community or spread across larger geographic areas, sometimes even becoming an epidemic or pandemic.

Sources

Sources are places where infectious agents (germs) live (e.g., sinks, surfaces, human skin). Sources are also called reservoirs.

Transmission

Transmission is a way germs move to the susceptible person. Germs depend on people, the environment and/or medical equipment to move in healthcare settings. Transmission is also called a pathway.

Susceptible Person

Susceptible Person is someone who is not vaccinated or otherwise immune. For example, a person with a weakened immune system who has a way for the germs to enter the body.

Colonization

Colonization is when someone has germs on or in their body but does not have symptoms of an infection. Colonized people can still transmit the germs they carry.

Infectious Diseases & Causes

Avian Influenza (Bird Flu)
Human infections with avian influenza (AI, or “bird flu”) are rare but do occur, most commonly after exposure to infected poultry (Bird-to-human spread). Limited person-to-person spread of bird flu is thought to have occurred rarely in the past, most notably with avian influenza A (H5N1). Based on this previous experience, some limited human-to-human spread of this H7N9 virus would not be surprising. Most important, however, is that this transmission not be sustained (ongoing).

Coronavirus
Human coronaviruses are common throughout the world. Seven different coronaviruses, that scientists know of, can infect people and make them sick. Human coronaviruses commonly cause mild to moderate illness in people worldwide. Two newer human coronaviruses, MERS-CoV and SARS-CoV, have been known to frequently cause severe illness.

Dengue Fever
Dengue is caused by any one of four related viruses transmitted by mosquitoes. There are not yet any vaccines to prevent infection with dengue virus and the most effective protective measures are those that avoid mosquito bites.

Ebola
Ebola, previously known as Ebola hemorrhagic fever, is a rare and deadly disease caused by infection with one of the Ebola virus strains. Ebola can cause disease in humans and nonhuman primates (monkeys, gorillas, and chimpanzees).

Measles (Rubeola)
Measles starts with fever, runny nose, cough, red eyes, and sore throat. It’s followed by a rash that spreads over the body. Measles is highly contagious and spreads through coughing and sneezing. Make sure you and your child are protected with measles, mumps, and rubella (MMR) vaccine.

Mpox
Mpox is a rare disease caused by infection with the monkeypox virus. Monkeypox virus is part of the same family of viruses as variola virus, the virus that causes smallpox. Monkeypox symptoms are similar to smallpox symptoms, but milder, and monkeypox is rarely fatal. Monkeypox is not related to chickenpox.

Seasonal Flu
Influenza (flu) is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness. Serious outcomes of flu infection can result in hospitalization or death. Some people, such as older people, young children, and people with certain health conditions, are at high risk for serious flu complications. The best way to prevent the flu is by getting vaccinated each year.

West Nile Virus
West Nile virus (WNV) is most commonly transmitted to humans by mosquitoes. You can reduce your risk of being infected with WNV by using insect repellent and wearing protective clothing to prevent mosquito bites.

Zika Virus
Zika Virus is another mosquito-borne illness like West Nile. You can reduce your risk of being infected with Zika by using insect repellent and wearing protective clothing to prevent mosquito bites. Pregnant women are particularly at risk of Zika, because the virus can cause birth defects in unborn infants.

How can we Prevent the Spread of Infectious Diseases?

There are several effective strategies to help prevent the spread of infectious diseases. Here are a few key practices to keep in mind:

Practice Good Hygiene – Wash your hands often with soap and warm water for at least 20 seconds, especially after coughing, sneezing, or being in public spaces.

Stay Home if You're Sick – Avoid going to work, school, or public places when you're feeling unwell to help protect others from getting sick.

Stay Up to Date on Vaccinations – Vaccines help protect you and those around you from many serious diseases.

Keep Surfaces Clean – Regularly disinfect high-touch surfaces like doorknobs, countertops, and phones.

Cough & Sneeze into your Sleeve – Always cough or sneeze into your sleeve or elbow—not your hands. This simple action helps keep others healthy and reduces the chance of spreading illness through touch.
Don't Share Personal Items – Avoid sharing personal items that can't be disinfected, like toothbrushes and razors, or sharing towels between washes. Needles should never be shared, should only be used once, and then thrown away properly.
Avoid Touching Wild Animals – You and your pets should avoid touching wild animals which can carry germs that cause infectious diseases. If you are bitten, talk to your doctor. Make sure that your pet's vaccinations are up-to-date.
Practice Safe Sex – Practicing safe sex helps protect against sexually transmitted infections (STIs) and diseases (STDs).