Why the measles surge could open the door to a host of other diseases

With measles making a comeback in many upper-income countries including the United States and still rampant in some poorer nations such as Democratic Republic of Congo and Madagascar, a leading measles expert is warning of a danger beyond the spread of the disease itself: There's mounting evidence that when a person is infected with measles, the virus also wipes out the immune system's memory of how to fight off all sorts of other life-threatening infections – ranging from gastro-intestinal bugs that cause diarrhea to respiratory viruses that trigger pneumonia.

"All of the sudden you end up having not just more outbreaks of measles, but you might have more outbreaks of rubella or flu or any number of other diseases," says Dr. Michael Mina, a Harvard professor who has authored some of the most ground-breaking research into this so-called "immune-amnesia" effect from measles. Mina says he plans to sound the alarm this weekend at a conference of vaccine researchers in Bilbao, Spain. In the poorest countries, he says, children could be at substantially greater risk of death.

For instance, say a two-year-old girl comes down with a particularly nasty case of flu – complete with a bout of pneumonia — but survives. In the process, her immune system learns how to produce antibodies against that particular virus. The next time the girl comes in contact with it, those antibodies would recognize the pathogen and quash it immediately.

But then imagine that, at age four, that same girl comes down with a case of measles that erases her immune system's record of how to produce antibodies against the flu strain she previously contracted. So if she encounters that particular flu virus again, she's back to square one – likely to come down with pneumonia all over again.

And just because she managed to survive the first time doesn't mean she'll survive again, adds Mina: "Every time we don't die from an infection we can basically think of it as, we got lucky." So by subjecting a child to the same infection a second time, "measles is basically making you play the lottery again."

Of course, in wealthier countries, children are far less likely to die of infections because they have access to better health care. But, says Mina, they're still subjected to other downsides, such as taking antibiotics that can trigger an adverse reaction or mess with the balance of bacteria in their gut.

Also, as more and more children lose immunity to diseases they fought off at a young age, those diseases could start raging through the wider population — not just children but the elderly and adults would be at risk. "We could see an increase in the transmission of all these pathogens that shouldn't be spreading past a certain age because normally kids are immune," says Mina.

Mina is careful to note that the notion that measles produces immune amnesia is still a hypothesis.

"But it's a hypothesis with really good data," he says.

For instance, back in the early 1960s, when the measles vaccine was first introduced on a mass scale in many countries, scientists observed that shortly afterward there was a massive drop in childhood deaths from not just measles but many other infections.

But it wasn't until 2015 that Mina and his collaborators were able to do a comprehensive statistical analysis of data reaching back to the 1940s. They found spikes in deaths from other childhood infections were directly predicted by measles outbreaks. And the effect lasted two to three years beyond the measles outbreak.

Since the publication of that finding — in the journal Science — researchers have found additional evidence for the immune amnesia hypothesis.

In 2018 a team led by Rik L. de Swart of Erasmus Medical Center in Rotterdam, Netherlands, found that children infected with measles in the United Kingdom were significantly more likely to suffer other infections requiring prescription of antibiotics in the two to five years following the measles infection.

Meanwhile, after decades of decline, measles cases have risen precipitously in recent years — due to a combination of hesitancy by parents in wealthier countries to vaccinate their children and a breakdown in the health infrastructure in less well-off nations. There have been massive outbreaks often involving tens of thousands of children in Brazil, India, the Philippines and Ukraine.

Last month the World Health Organization announced that four European countries – Albania, the Czech Republic, Greece and the U.K. – had all lost their previous measles-free status due to local outbreaks. This spring the number of cases in the United States topped 1,000 for the first time in more than two-and-half decades. And globally the total number of cases rose by 300 percent in the first quarter of 2019 compared to the same period in 2018.

Mina says if the immune amnesia hypothesis is correct, it's only a matter of time before the recent surge in measles infections produces a concurrent surge in other diseases. But he's urging public health officials not to wait to find out: If someone has been infected with measles, he says, "I think we should consider giving them all their childhood vaccines all over again."

Copyright 2019 NPR. To see more, visit https://www.npr.org.

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