An epidemic is defined by the Centers of Disease Control and Prevention (CDC) as a sudden increase in the number of cases of an infectious disease within a community or geographic area during a specific time period.

A spike in the number of cases of the same illness in an area beyond what health officials expect to see is an outbreak. The terms may be used interchangeably, though epidemics are often considered more widespread.

Over the years, many outbreaks of infectious diseases have occurred and spread across the United States.

Smallpox came to North America in the 1600s. Symptoms included high fever, chills, severe back pain, and rashes. It began in the Northeast and the Native American population was ravaged by it as it spread to the west.

In 1721, more than 6,000 cases were reported out of a Boston population of 11,000. Around 850 people died from the disease.

In 1770, Edward Jenner developed a vaccine from cow pox. It helps the body become immune to smallpox without causing the disease.

Now: After a large vaccination initiative in 1972, smallpox is gone from the United States. In fact, vaccines are no longer necessary.

One humid summer, refugees fleeing a yellow fever epidemic in the Caribbean Islands sailed into Philadelphia, carrying the virus with them.

Yellow fever causes yellowing of the skin, fever, and bloody vomiting. During the 1793 outbreak, it’s estimated that the 10 percent of the city’s population died and many others fled the city to avoid it.

A vaccine was developed and then licensed in 1953. One vaccine is enough for life. It’s mostly recommended for those 9 months and older, especially if you live or travel to high risk areas.

You can find a list of countries where the vaccine is recommended for travel on the Centers for Disease Control and Prevention (CDC) website.

Now: Mosquitoes are key to how this disease spreads, particularly in areas such as Central America, South America, and Africa. Eliminating mosquitoes has been successful in controlling yellow fever.

While yellow fever has no cure, someone who does recover from the illness becomes immune for the rest of their life.

The United States had three serious waves of cholera, an infection of the intestines, between 1832 and 1866. The pandemic began in India and swiftly spread across the globe through trade routes.

New York City was the first U.S. city to feel the impact. Between 5 and 10 percent of the total population died in large cities.

It’s unclear what ended the pandemic, but it may have been the change in climate or the use of quarantine measures. By the early 1900s, outbreaks had ended.

Immediate treatment is crucial because cholera can cause death. Treatment includes antibiotics, zinc supplementation, and rehydration.

Now: Cholera still causes nearly 95,000 deaths a year worldwide, according to the CDC. Modern sewage and water treatment have helped eradicate cholera in some countries, but the virus is still present elsewhere.

You can get a vaccine for cholera if you’re planning to travel to high risk areas. The best way to prevent cholera is to wash your hands regularly with soap and water and avoid drinking contaminated water.

Scarlet fever is a bacterial infection that can occur after strep throat. Like cholera, scarlet fever epidemics came in waves.

Scarlet fever most commonly affects children ages 5 to 15. It’s rare in children under 3. Adults who are in contact with sick children have an increased risk.

Older studies argue that scarlet fever declined due to improved nutrition, but research shows that improvements in public health were more likely the cause.

Now: There’s no vaccine to prevent strep throat or scarlet fever. It’s important for those with strep throat symptoms to seek treatment quickly. Your doctor will typically treat scarlet fever with antibiotics.

One of the biggest typhoid fever epidemics of all time broke out between 1906 and 1907 in New York.

Mary Mallon, often referred to as “Typhoid Mary,” spread the virus to about 122 New Yorkers during her time as a cook on an estate and in a hospital unit.

About 5 of the 122 New Yorkers who contracted the virus by Mary Mallon died. The CDC cites a total of 13,160 deaths in 1906 and 12,670 deaths in 1907.

Medical testing showed that Mallon was a healthy carrier for typhoid fever. Typhoid fever can cause sickness and red spots to form on the chest and abdomen.

A vaccine was developed in 1911, and an antibiotic treatment for typhoid fever became available in 1948.

Now: Today typhoid fever is rare. But it can spread through direct contact with people who have the virus, as well as consumption of contaminated food or water.

H1N1 is a strain of flu that still circulates the globe annually.

In 1918, it was the type of flu behind the influenza pandemic, sometimes called the Spanish flu (though it didn’t actually from come Spain).

After World War I, cases of the flu slowly declined. None of the suggestions provided at the time (wearing masks, drinking coal oil) were effective cures. Today’s treatments include bed rest, fluids, and antiviral medications.

Now: Influenza strains mutate every year, making last year’s vaccinations less effective. It’s important to get your yearly vaccination to decrease your risk for the flu.

Diphtheria peaked in 1921, with 206,000 cases. It causes swelling of the mucous membranes, including in your throat, that can obstruct breathing and swallowing.

Sometimes a bacterial toxin can enter the bloodstream and cause fatal heart and nerve damage.

By the mid-1920s, researchers licensed a vaccine against the bacterial disease. Infection rates plummeted in the United States.

Now: Today more than 80 percent of children in the United States are vaccinated, according to the CDC. Those who contract the disease are treated with antibiotics.

Polio is a viral disease that affects the nervous system, causing paralysis. It spreads through direct contact with people who have the infection.

Outbreaks occurred regularly in the United States through the 1950s, with two major polio outbreaks in 1916 and in 1952. Of the 57,628 reported cases in 1952, there were 3,145 deaths.

In 1955, Dr. Jonas Salk’s vaccine was approved. It was quickly adopted throughout the world. By 1962, the average number of cases dropped to 910. The CDC reports that the United States has been polio-free since 1979.

Now: Getting vaccinated is very important before traveling. There’s no cure for polio. Treatment involves increasing comfort levels and preventing complications.

A major flu outbreak occurred again in 1957. The H2N2 virus, which originated in birds, was first reported in Singapore in February 1957, then in Hong Kong in April 1957.

It appeared in coastal cities in the United States in the summer of 1957.

The estimated number of deaths was 1.1 million worldwide and 116,000 in the United States.

This pandemic is considered to be mild because it was caught early. Scientists were able to develop a vaccine based on the knowledge from creating the first flu vaccine in 1942.

Now: H2N2 no longer circulates in humans, but it still infects birds and pigs. It’s possible that the virus may again jump from animals to humans in the future.

Measles is a virus that causes fever, runny nose, cough, red eyes, and sore throat, and later a rash that spreads over the whole body.

It’s a very contagious disease that spreads through the air. Almost all children caught measles prior to the vaccine. In the second part of the 20th century, most cases were due to inadequate vaccination coverage.

Doctors began to recommend a second vaccine for everyone. Since then, each year has typically had fewer than 1,000 cases, though this was surpassed in 2019.

Now: The United States has experienced smaller outbreaks of measles in recent years. The CDC states that unvaccinated travelers who visit abroad can contract the disease. When they come home to the United States, they pass it on to others who aren’t vaccinated.

Be sure to get all the vaccinations your doctor recommends.

One of Milwaukee’s two water treatment plants became contaminated with cryptosporidium, a parasite that causes the cryptosporidiosis infection. Symptoms include dehydration, fever, stomach cramps, and diarrhea.

An initial study indicated 403,000 people became ill and 69 people died, according to the Water Quality & Health Council, making it the largest waterborne outbreak in United States history.

Most people recovered on their own. Of the people who died, the majority had compromised immune systems.

Now: Cryptosporidiosis is still a yearly concern. The CDC reports that cases increased by 13 percent per year between 2009 and 2017. The number of cases and outbreaks vary in any given year.

Cryptosporidium spreads through soil, food, water, or contact with contaminated feces. It’s one of the most common causes of illness to occur through summer recreational water use and can easily be spread from farm animals or in childcare settings.

Be sure to practice good personal hygiene, such as washing hands, when camping, or after touching animals. Refrain from swimming if you have diarrhea.

In the spring of 2009, the H1N1 virus was detected in the United States and spread quickly across the country and the world. This outbreak made headlines as the swine flu.

The CDC estimates that there were 60.8 million cases, 274,304 hospitalizations, and 12,469 deaths in the United States.

Globally, 80 percent of this outbreak’s deaths were estimated to have occurred in people younger than 65.

In late December 2009, the H1N1 vaccine became available to everyone who wanted it. Virus activity levels began to slow.

Now: The H1N1 strain still circulates seasonally, but it causes fewer deaths and hospitalizations. Influenza strains mutate every year, making the previous year’s vaccinations less effective. It’s important to get your yearly vaccination to decrease your risk for the flu.

Pertussis, known as whooping cough, is highly contagious and one of the most commonly occurring diseases in the United States. These coughing attacks can last for months.

Infants too young for vaccination have the highest risk for life-threatening cases. During the first outbreak, 10 infants died.

A whooping cough outbreak comes every 3 to 5 years. The CDC reports that an increase in the number of cases will likely be the “new normal.”

Now: The occurrence of the disease is much less than it was. The CDC recommends all people need the vaccine, but that pregnant women get a vaccination during the third trimester to optimize protection at birth.

It’s also recommended that all children, and anyone who hasn’t previously been vaccinated, get the vaccine.

First documented in 1981, the epidemic known today as HIV appeared to be a rare lung infection. Now we know that HIV damages the body’s immune system and compromises its ability to fight off infections.

AIDS is the final stage of HIV and, according to the CDC, in 2018 it was the 9th leading cause of death in the United States among people 25 to 34 years old. Just because a person gets HIV doesn’t mean they’ll develop AIDS.

HIV may be transmitted sexually or through blood or body fluids from person to person. It can be transmitted from mother to unborn baby if not treated.

Pre-exposure prophylaxis (or PrEP) is a way for high risk populations to avoid HIV infection before exposure. The pill (brand name Truvada) contains two medicines that are used in combination with other medicines to treat HIV.

When someone is exposed to HIV through sexual activity or injection drug use, these medicines can work to keep the virus from establishing a permanent infection.

The CDC believes that for the first time in modern history, the world has the tools to control the HIV epidemic without a vaccine or cure, while laying the groundwork to eventually end HIV.

Controlling the epidemic requires reaching high risk groups with treatment and prevention.

Now: While there’s no cure for HIV, transmission risk can be decreased through safety measures, like making sure needles are sterilized and having sex with barrier methods.

Safety measures can be taken during pregnancy to prevent the syndrome from being transmitted from mother to child.

For emergencies, PEP (post-exposure prophylaxis) is a new antiretroviral medicine that prevents HIV from developing within 72 hours.

The SARS-CoV-2 virus, a type of coronavirus that causes the disease COVID-19, was first detected in Wuhan City, Hubei Province, China in late 2019. It seems to spread easily and sustainably in the community.

Cases have been reported all over the world, and as of late May 2020, there were over 1.5 million cases and over 100,000 deaths in the United States.

The disease can be life threatening, and older adults and people who have preexisting medical conditions, like heart or lung disease or diabetes, seem to be at higher risk for developing more serious complications.

There’s currently no vaccine.

Primary symptoms include:

  • fever
  • dry cough
  • shortness of breath
  • fatigue

Education

Educating yourself about current disease outbreaks can help you understand what precautions you should take in order to keep you and your family safe and healthy.

Take the time to search for ongoing epidemics by visiting the CDC’s Current Outbreak List, especially if you’re traveling.

Protect yourself and your family

The good news is that most outbreaks listed here are rare and, in some cases, preventable. Make sure your family is up to date on their vaccinations before traveling, and get the latest flu vaccines.

Simple steps in the kitchen and food safety techniques can also prevent you and your family from contracting or transferring infections.