The Ebola virus has been causing panic in the United States, but gears have now been switched, and Americans are focusing on the increasing amount of measles cases.

This year marks the worst outbreak of measles in 20 years, reports CNN, infecting 593 people in at least 21 different states. In Ohio alone, there are already 377 cases, which began when unvaccinated travellers visited the Philippines, stated the Ohio Department of Health (ODH).   

Measles is a highly contagious, viral respiratory disease that, if left untreated, can be fatal. The measles virus resides in the mucus of infected people. When they sneeze or cough, infected droplets remain active for up to 2 hours, according to the ODH.

The severity of measles can be prevented through a vaccine called MMR, which stands for Measles-Mumps-Rubella. The ODH recommends that Ohio residents, especially young children, along with anyone who is unvaccinated, receive the shot to prevent the spread of the disease.    

Jennifer Shih, a pediatric and adult allergist and immunologist at Emory University, is particularly concerned with the growing number of infected people, especially because her 2-year-old twins are too young to receive the vaccination, according to CNN.

"We can't know for sure that the anti-vaccine movement, led by uninformed celebrities and discredited research, is the reason we are having such a terrible measles outbreak in the United States. But certainly it's not helping our children," Shih said.

Shih refers to Jenny McCarthy, who claimed that certain vaccinations were more likely to cause autism, which deferred other people from receiving the vaccination.

Before a vaccine was made available in the U.S., measles infected 500,000 people annually, resulting in about 500 deaths per year, writes CNN. 1994 was the pivotal year that vaccinations were introduced, which decreased the number of infections from 500,000 to a mere 60 cases.

After the vaccine was created, measles was close to being completely eradicated in the U.S. and the CDC predicted that they had saved the lives of 732,000 people.

Measles, however, much like Ebola, is making a fierce comeback, and the number of cases keeps rising since its reappearance in 2010.  The CDC believes that the outbreaks are attributed to unvaccinated U.S. citizens who contract measles while abroad, and bring the disease back to infect those not vaccinated in the U.S., according to CNN.