Measles cases are increasing in the United States. Here is what you need to know.

Number of measles United States has reached the second highest level in 25 years – and this is only in April.

As the disease spreads to new states and the number of cases is expected to increase, here's what you need to know about infection, current outbreaks, and ways to protect yourself.

Measles is "one of the most contagious infections known," according to Dr. Aaron Milstone and Lisa Maragakis, infectious disease specialists at Johns Hopkins. The disease is caused by a virus that spreads in the air.

"Nine out of 10 unimmunized children who come into contact with an infected person will contract the virus," according to doctors. "The virus can stay in the air for about two hours after a person with measles has left the room."

Measles can cause fever, a runny nose and small red bumps all over the body. In the most severe cases, the disease can weaken the immune system, resulting in complications such as pneumonia and encephalitis, or even death.

There is no prescription medication for measles. But two doses of MMR vaccine, which protects against measles, mumps and rubella, are effective at about 97% in measles prevention, according to US Centers for Disease Control and Prevention.

To date, 555 measles cases have been reported in 2019, according to numbers published on April 11 by the CDC.

Arizona, California, Colorado, Connecticut, Florida, Georgia, Illinois, Indiana, Kentucky, Maryland, Massachusetts, Michigan, Missouri, Nevada New Hampshire, New Jersey, New York State, Oregon and Washington have reported cases of measles.

Outbreaks of measles, defined as three or more cases in a given area, are currently continuing in Rockland County in New York, in Clark County in Washington State, in Ocean County. in New Jersey, in Oakland County in Michigan and in several counties of California.

The majority of recent outbreaks have been associated with travelers reporting measles from countries with a higher measles epidemic, including Israel, Ukraine and the Philippines. The measles cases of recent years also come from common destinations such as England, France, Germany and India.

The Democratic Republic of the Congo, Ethiopia, Georgia, Kazakhstan, Kyrgyzstan, Madagascar, Myanmar, the Philippines, Sudan, Thailand and Ukraine are currently experiencing widespread epidemics.

The epidemic in Madagascar, the largest in the country's history, has killed more than 1,200 people, most of them children. The Associated Press recently reported.

The majority of people who contract measles are not vaccinated. A person who has received two doses of MMR vaccine is considered immune and never needs to receive a booster shot, according to the CDC. However, the agency recommends that people who are unsure of their immunity or who can not locate their vaccination record to consider being vaccinated again without risk.

In the United States, it is increasingly common not to be vaccinated against measles for themselves and their children because of their religious beliefs and personal preferences. Much of the anti-vaccination movement was fueled by unfounded fears about side effects, including the conspiracy theory that the MMR vaccine was linked to autism. This belief has been largely engendered by a study denied 1998 based on only 12 patients and led by a doctor who was found to have falsified data. Several long-term studies have shown no link between measles vaccine and autism.

However, some parts of the population can not receive the vaccine for medical reasons. The vaccine is usually not given to infants under 1 year old, in part because it is not considered effective at this age. In addition, people who are immunocompromised do not usually receive vaccines, which makes them more vulnerable to infection if they are exposed to the disease.

This is why doctors insist on the importance of getting vaccinated, not only to protect themselves but also to strengthen the "collective immunity" defined by the American Academy of Pediatrics, as the whole of the immunity of which benefit individuals "by living in a community where many people are vaccinated. "

Seventeen states allow exemptions for religious and philosophical immunization in schools, according to the National Conference of State Legislatures. Many other states allow religious but not philosophical exemptions. Only three states – California, Mississippi and West Virginia – offer no non-medical exemption.

Lawmakers from Maine, Oregon and Washington are currently considering legislation to end non-medical exemptions to vaccination requirements.

The New York City Department of Health recently ordered mandatory measles vaccination in parts of Brooklyn to combat the growing epidemic of the disease.