With nearly 700 measles cases this year, the CDC is bracing for the disease to grab a 'foothold' on the US again - for the first time in decades

• The measles, a highly contagious viral infection that was deemed eradicated in the US in 2000, is back and spreading fast.
• So far this year, 695 measles cases have been reported in 22 states, according to the CDC. That is already more cases than the country has seen in any year since 2000.
• A major outbreak in New York City is ongoing, and it has sickened 334 people in pockets of Brooklyn and Queens, where many Orthodox Jewish children are unvaccinated.
• The measles virus is very contagious; it can live on surfaces for two hours outside the human body.
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The measles, a highly-contagious, deadly viral infection that was deemed eliminated in the US in 2000, is spreading once again.

So far this year, 695 measles cases have been reported in 22 states. That is the highest measles case count the country has seen in at least 19 years.

The US Centers for Disease Control and Prevention is now warning that "the longer these outbreaks continue, the greater the chance measles will again get a sustained foothold in the United States."

Though most Americans are protected against measles with routine measles, mumps, rubella (MMR) vaccinations, the measles is infecting scores of children clustered in pockets of the country where not everyone is getting their shots.

"Measles is not a harmless childhood illness, but a highly contagious, potentially life-threatening disease," US Health and Human Services Secretary Alex Azar said in a statement on Wednesday.

The measles virus is very contagious: it can live on surfaces for two hours outside the human body, quietly infecting other people long after a sick person is gone. The illness prompts high fevers above 104 degrees Fahrenheit, a hacking cough, runny nose, sore throat, eye infections, and eventually red, itchy raised bumps develop on the skin. There is not much parents can do to treat measles other than let the virus run its course. In rare cases, the illness can lead to brain swelling, blindness, deafness, and even death.

Dr. Amesh Adalja at the Johns Hopkins Center for Health Security said there's a simple reason that measles outbreaks are on the rise again in the US.

"In earlier eras, it was kind of the norm to be vaccinated. It wasn't something that people questioned," Adalja told Business Insider. "But in the wake of the false links to autism that occurred in the mid 1990s, that whole celebrity culture picking up these false stories, we ended up in this type of a mess."

Read more: Even if you got the measles vaccine, you may not be protected against the disease - here's how to tell

One large outbreak that started in the Pacific Northwest earlier this year sickened at least 73 people there and seems to have run its course. But another large outbreak in New York City is ongoing, and with 94 new infections so far this month, an average of near four new measles cases are being reported every day. (Vox reported that the Orthodox Jewish community in Brooklyn has been the target of anti-vaccination literature, and many cases have been children within this community.)

Earlier this month, the New York City health commissioner ordered that every unvaccinated person living in the Williamsburg neighborhood of Brooklyn (who is not medically exempt) must get a measles vaccine, or show proof of immunity. If they don't, Williamsburg residents can face the possibility of a $1,000 fine. Another large measles outbreak outside the city in New York state has sickened an additional 232 people.

No deaths have been reported yet in the US, but considering that roughly two out of every 1,000 kids who get the measles will die, many public health experts say it may only be a matter of time.

"It's going to be unfortunate because as we get to closer to a thousand cases, we are likely to start seeing more severe cases, and maybe even a death," Adalja said. "Unfortunately, that may be what it takes to get people to realize that this is not something that they should take lightly."

In other places around the globe, children are rapidly dying from the measles already. On the island of Madagascar off the east coast of Africa, more than 1,200 people have died of measles since October, in that country's largest outbreak in history. Some mothers there have gladly lined up to get their kids shots.

In the US, the measles vaccine, which is 97% effective, has been a childhood staple since it was first developed in 1963. Before then, measles was a common childhood ailment that nearly every kid suffered through. It would kill 400 to 500 people every year in the US. Today's smaller measles outbreaks in the US often start when someone brings a case of the illness back with them after traveling abroad.

"We've got measles outbreaks in places like Israel, and France, and Italy, and people travel back and forth there all the time," Adalja said. "That's what's sparking these outbreaks."

In 2000, the Centers for Disease Control and Prevention said measles was effectively eliminated in the US because the virus was not being transmitted year-round and there were fewer than 100 cases per year.