View of Marigot Bay with yachts, Castries, St. Lucia island, Lesser Antilles, Windward Islands, St. Lucia
Cruise ship quarantined in port over measles concerns
00:34 - Source: HLN
CNN  — 

A series of measles cases in the United States has led to fear and uncertainty in some communities, as well as quarantines at sea and at universities. Some cases have even hit adults who thought they were protected by the vaccine.

Even the Avengers could hardly be prepared for the threat, with moviegoers in California facing possible exposure to the virus. Same for some travelers at multiple airports across the country.

In 2019, the US has seen the highest number of confirmed cases since disease was declared eliminated in 2000. Some officials across the country have declared states of emergency.

How contagious is it?

“Measles is one of the most highly contagious diseases known,” said Dr. Julia S. Sammons, a pediatric infectious disease specialist and medical director of the Department of Infection Prevention and Control at the Children’s Hospital of Philadelphia.

Once a person has measles, about 90% of close contacts who are susceptible to it will develop the disease, she added.

The measles virus spreads through coughing and sneezing. Afterward, it can linger in the air for up to two hours. If someone who is not immune to the virus breathes the air or touches an infected surface, they can become infected, according to the US Centers for Disease Control and Prevention.

How do I know if I have measles and not just a cold or the flu?

Early on, measles can be confused for other viral illnesses such as the flu. But the red blotchy rash that comes with it may help set it apart.

“Imagine that you have a bucket of rash. If you pour that bucket of rash over your head, the rash sort of cascades down,” Sammons said. “So the rash starts over the head, typically over the scalp, and then it spreads down head to toe.”