By Mark Lieber, CNN
(CNN) -- The 2018 FIFA World Cup is kicking off in Russia in only a week. Soccer fans may be eager to catch a glimpse of Cristiano Ronaldo and other world-renowned players, but there's one thing they definitely don't want to catch: measles.
Measles is a highly infectious -- and potentially fatal -- viral illness that is typically spread by breathing or coughing. Waning levels of vaccine coverage in recent years have led to outbreaks across parts of Europe, including Russia, according to Robb Butler, program manager for vaccine-preventable diseases at the World Health Organization's Regional Office for Europe.
"Over the last decade, we've certainly seen a resurgence of vaccine preventable diseases in the European region, and measles is one of them," Butler said. "In 2017, we had a fourfold increase (in measles), and that seems to be continuing into 2018."
In 2017, over 20,000 people across Europe were infected with the virus, resulting in at least 35 deaths. Among the hardest-hit nations were Ukraine and Romania. Romania reported over 5,000 cases in 2017, according to Butler.
Russia has also been heavily affected by the recent outbreak, with more than 800 cases reported in 2018. There have been no measles-related deaths reported there this year, according to Butler.
"We do have measles circulating in the Russian Federation at the moment," Butler said. "And that really stresses the importance of vulnerability and the risk that everybody runs if they do not check their status and get vaccinated."
Children and adults who are traveling to Russia for the World Cup -- which takes place between June 14 and July 15 -- should therefore make sure that they have received two doses of the measles vaccine, he said.
"At the World Cup, we have countries that are endemic to measles and many countries that have recently had large-scale outbreaks, such as Germany and Brazil. So it's very important that individuals check their status before they travel," he said.
Symptoms of measles include a runny nose, high fever, eye inflammation and a rash that starts on the face and spreads to the rest of the body. Complications such as blindness, brain inflammation and even death can occur in approximately 30% of cases, according to WHO.
The disease is also highly contagious, according to Dr. William Schaffner, an infectious disease specialist at the Vanderbilt School of Medicine.
"Measles is the most highly infectious virus that we know of and can be transmitted fairly readily to susceptible individuals," Schaffner said. "The measles virus can hover in the air and be infectious for hours afterward."
For those who become ill, treatment normally consists of symptom management, according to Schaffner.
"What you have to do is, first of all, manage their airway and give them good fluid replacement so they don't get dehydrated," Schaffner said. "And if they're beginning to get pneumonia -- that's frequently a complicated bacterial pneumonia -- they would need antibiotics in that circumstance, as well."
The measles vaccine is often given as part of the combined measles, mumps and rubella (MMR) vaccine. The vaccine is typically given in two doses in early childhood. Adults who do not have immunity to the disease should also receive the vaccine, according to Dr. Diane Griffin, a professor of molecular microbiology and immunology at Johns Hopkins Bloomberg School of Public Health.
"We actually have a fairly substantial proportion of people who are adults who do not have a history of measles as a child and may have missed getting two doses of the vaccine because that recommendation is relatively recent," Griffin said.
One dose of the vaccine is about 93% effective at preventing measles if the person is exposed to the virus, while two doses are about 97% effective, according to the US Centers for Disease Control and Prevention.
Though the disease is no longer endemic in the United States, an outbreak in 2014 affected about 125 people, most of whom did not have the full two-dose vaccination series, according to the CDC.
Measles was once a widespread disease that killed 2 million to 3 million people worldwide every year, according to WHO. The prevalence dropped dramatically after the introduction of the vaccine in 1963, according to Griffin.
However, due to a combination of factors -- including the anti-vaccine movement and a deterioration in some health systems -- outbreaks have increased over the past decade, Butler said.
"Measles is particularly alarming because, not only does it indicate that we've got susceptible populations ... but also, it's a good proxy indicator for failures in health care delivery, because measles is incredibly contagious, and it really does expose any weakness in health systems," Butler said.
And due to the high density of people attending from different countries, the World Cup could provide a perfect environment for a measles outbreak, according to Griffin.
"Big sports events have huge numbers of people that come from all over the world," Griffin said. "And all you need is one or two people that are incubating measles, and they can spread it fairly easily in all the different places that people go."
Consequently, those planning to attend the games should make sure to get the vaccine if they are not already immunized, to protect both themselves and others in their home communities, according to Butler.
"It's very important that individuals check their status before they travel so they don't contract the disease at the World Cup or, worse, that they don't bring it into their home communities and import it into countries that may have already eliminated the disease," Butler said.
"But it's important that everybody make sure they are vaccinated, whether they are going to the World Cup or not," he added.
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