Health officials are raising alarm about the spread of measles in the United States and across the globe.
On Monday, the Centers for Disease Control and Prevention released a health advisory urging people over the age of 6 months who are traveling internationally to get vaccinated against the highly infectious virus. The agency also said that anyone returning to the United States from abroad should watch out for measles symptoms for three weeks after they arrive home.
Here’s what to know about how the virus spreads and what its symptoms look like.
How and when measles spreads
Part of what makes measles so tricky to contain is that infected people can easily spread the virus before even realizing they have it. Someone with measles can transmit the infection for up to four days before developing a telltale rash, according to the C.D.C.
Measles spreads when someone who is sick coughs or sneezes, said Dr. Paul Offit, a vaccine expert at the Children’s Hospital of Philadelphia. The virus can linger in the air for up to two hours after an infected person leaves a room. People can also contract measles by touching a surface that a sick person has contaminated and then touching their eyes, nose or mouth. “It’s the most contagious of the vaccine-preventable diseases,” Dr. Offit said.
Symptoms to watch out for
It typically takes one to two weeks for someone to feel ill after coming into contact with the virus. The earliest symptoms tend to be a cough, runny nose, pink eye and a fever. Some people may have a fever that goes above 104 degrees, which can be particularly dangerous for young children. Fewer than one in every 10 people with measles will also develop diarrhea, according to the agency.
“It’s a pretty miserable disease,” said Dr. Sean O’Leary, a professor of pediatric infectious diseases specialist at the University of Colorado School of Medicine.
Two to three days after symptoms first appear, people with measles can develop tiny white spots inside the mouth, sometimes called Koplik spots. A rash breaks out across the skin, typically around a day or two later, often starting as flat red spots on the face that then spread to the neck, torso, arms, legs and feet. The rash usually fades after around six days, according to the World Health Organization. The C.D.C. recommends that people isolate for four days after they develop a rash, since they can remain contagious for that period of time.
Most cases of measles are mild, but the virus can lead to severe complications, especially in infants, very young children and people with compromised immune systems. The disease can be fatal. Pregnant women who are not vaccinated and contract measles can give birth prematurely or have a baby with a low birth weight. One in about every 10 children with measles will develop an ear infection. Measles can also lead to pneumonia, which is the most common cause of death from measles in young children, and it can cause blindness. Children can also develop brain swelling that can lead to deafness or intellectual disabilities.
Vaccination is the best way to protect against the disease, Dr. Offit said. Doctors typically recommend that children be vaccinated starting at age 1, although they can get vaccinated earlier in some cases. The C.D.C. advisory encouraged parents traveling internationally to vaccinate babies older than 6 months.
Some people with compromised immune systems, like those receiving chemotherapy, may not be able to get vaccinated. But for those who can get vaccinated, protection typically can last a lifetime, he said — and it’s never too late to get the shots.