The number of new U.S. measles cases continued to accelerate last week as health authorities race to curb the outbreaks and scientists who study the virus say measles may be more harmful than once believed.
There have been 555 cases of measles in 20 states across the U.S. this year as of April 11, the Centers for Disease Control and Prevention reported Monday, 90 more than were reported the previous week.
The increase in cases means 2019 could soon become the worst for measles in the U.S. since the disease was officially eliminated—meaning that it stopped circulating continuously—in 2000. In 2014, the worst year since elimination, 667 cases were reported.
The U.S. outbreaks this year are among the latest to emerge in developed countries, where high overall vaccination rates and access to health care make death from measles uncommon. Measles complications and deaths are a greater threat in poorer regions of the world, where inadequate nutrition and greater exposure to other infections can make it harder to fight off effects of measles.
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The virus continues to flare up in the U.S. among groups whose vaccination rates are low, often after exposure to overseas travelers who return with the disease. An outbreak among Orthodox Jews in New York City this year has led to a surge in U.S. cases. New York City health officials said Friday that there have been 285 measles cases in the city, and more than 11,000 people have been exposed to the virus.
Researchers who study the virus say that concern about these outbreaks extends beyond the effect of the initial infection to longer-term implications for the health of the victims.
The virus may leave the immune system in a temporary state of amnesia, leaving the body’s defenses unable to remember and effectively attack some invaders it has seen before, according to emerging research. Immune-system memory loss could leave the body prone to more severe infections for two to three years, until it relearns from hard-won experience how to fend off attackers, researchers have said.
“You don’t have that quick response,” said Michael Mina, an assistant professor at Harvard University who studies immune-system response to the virus. “You have to create it from scratch again.”
Measles is highly contagious, infecting up to 90% of those who are susceptible. It can have complications and long-term effects. About one-third of children who develop measles will have complications, including diarrhea, pneumonia or ear infections. Some complications, though rare, are serious: about one in 1,000 people in the U.S. with measles develop encephalitis, or brain inflammation, that can develop a week or two after a rash appears and leave the victim deaf or with an intellectual disability.
Measles can also lead to another serious complication: subacute sclerosing panencephalitis, a rare disease of the central nervous system that is usually fatal. It occurs usually seven to 10 years after someone has the measles.
“We can’t tell you if your individual child is going to do well or not well with measles,” said Thomas Clark, deputy director of the CDC’s division of viral diseases. “That’s why we vaccinate every child.”
The immune-system amnesia research, though developing, could help explain evidence suggesting measles vaccination helps reduce risks of other infections, said public-health and infectious-disease experts. Advisers to the World Health Organization found studies, though largely observational, that point to such a benefit, they said in 2014.
Death rates from measles have plunged with vaccination. Still, global deaths may be higher than recorded if the virus creates amnesia in the immune system for an extended period and leaves the body at risk for more severe infections from other pathogens, researchers said.
One 2015 study that suggested long-term harm to the immune system closely examined death rates among children before and after arrival of measles vaccines in the U.S., Denmark, England and Wales.
Memory Loss
Research suggests the measles virus erases immune-system memories by killing cells that help the body remember harmful bugs and how to fight them.
The measles virus lingers in the air, where it is inhaled by passersby.
The measles virus hijacks the immune-system memory cells in order to reproduce, killing them in the process.
3
1
Measles
Virus
Other immune cells arrive to fight the measles virus, also killing off immune-system memory cells.
4
The immune-system sentinels, known as dendritic cells, shuttle the virus to the lymph nodes, where it can be screened by immune-system memory cells.
2
Dendritic cells
Measles circulates in the body, eventually hijacking lung cells to further reproduce. It proliferates in the lungs and is coughed in the air, where it is inhaled by a passerby.
5
Memory cells
Source: Michael Mina Harvard University; Gerben Ferwerda, Radboud University Medical Centre
The measles virus lingers in the air, where it is inhaled by passersby.
The measles virus hijacks the immune-system memory cells in order to reproduce, killing them in the process.
3
1
Measles
Virus
Other immune cells arrive to fight the measles virus, also killing off immune-system memory cells.
4
The immune-system sentinels, known as dendritic cells, shuttle the virus to the lymph nodes, where it can be screened by immune-system memory cells.
2
Dendritic cells
Measles circulates in the body, eventually hijacking lung cells to further reproduce. It proliferates in the lungs and is coughed in the air, where it is inhaled by a passerby.
5
Memory cells
Source: Michael Mina Harvard University; Gerben Ferwerda, Radboud University Medical Centre
The measles virus lingers in the air, where it is inhaled by passersby.
The measles virus hijacks the immune-system memory cells in order to reproduce, killing them in the process.
3
1
Measles
Virus
Other immune cells arrive to fight the measles virus, also killing off immune-system memory cells.
4
The immune-system sentinels, known as dendritic cells, shuttle the virus to the lymph nodes, where it can be screened by immune-system memory cells.
2
Dendritic cells
Measles circulates in the body, eventually hijacking lung cells to further reproduce. It proliferates in the lungs and is coughed in the air, where it is inhaled by a passerby.
5
Memory cells
Source: Michael Mina Harvard University; Gerben Ferwerda, Radboud University Medical Centre
The measles virus lingers in the air, where it is inhaled by passersby.
1
Measles
Virus
The immune-system sentinels, known as dendritic cells, shuttle the virus to the lymph nodes, where it can be screened by immune-system memory cells.
2
Dendritic cells
Memory cells
The measles virus hijacks the immune-system memory cells in order to reproduce, killing them in the process.
3
Other immune cells arrive to fight the measles virus, also killing off immune-system memory cells.
4
Measles circulates in the body, eventually hijacking lung cells to further reproduce. It proliferates in the lungs and is coughed in the air, where it is inhaled by a passerby.
5
Source: Michael Mina Harvard University; Gerben Ferwerda, Radboud University Medical Centre
Before widespread vaccination, researchers found the incidence of measles strongly predicted childhood deaths from other infectious diseases in the next 28 months to 35 months, said Dr. Mina, one of the study’s authors. “It’s like a shadow.”
When vaccination slashed the incidence of measles, childhood deaths from other infectious diseases plunged too, according to the study, which was published in the journal Science.
Improved health care in the U.S. would likely now prevent those deaths, Dr. Mina said. But a separate study of children ages 1 to 15 in the U.K. between 1990 and 2014 found children who recover from measles are also more likely to be diagnosed with later infections and need prescription medication.
The study’s results suggests the cost of measles outbreaks may be higher than public-health investments to contain the disease. As of late March, Washington state’s public-health spending to contain an outbreak that had infected 74 people as of April 10 had totaled more than $1 million, said Dr. Scott Lindquist, epidemiologist for communicable diseases with the Washington State Department of Health.
U.S. pediatricians and public-health officials said the research hasn’t changed how they monitor measles patients. Pediatricians should already keep a close eye on children who get measles for further complications, said Sean O’Leary, a pediatric-infectious-disease specialist who helps draft practice recommendations for the American Academy of Pediatrics.
“Measles is a really bad disease in a lot of ways, and this is one of the ways,” he said of subsequent complications.
To further explore how measles could weaken the immune system for two or three years, researchers are studying what happens when the virus infiltrates the body.
During an infection, viruses hijack cells inside the body to reproduce. Viruses get inside cells by finding ones with unique receptors, or cellular docks, they can exploit. Measles specifically targets receptors found on immune-system cells, including memory cells that recall prior infections so the body’s defenses can respond more efficiently. The virus kills those cells as it propagates. Meanwhile, other immune-system cells attack memory cells that host the virus to halt the infection.
Depleted immune-system memory cells could leave the body unable to recall and forcefully respond to invaders it has seen before, said Rik de Swart, a virologist at Erasmus MC, University Medical Center in Rotterdam in the Netherlands, whose research illuminated the process in monkeys using fluorescent cells. “It clears out the measles,” Dr. de Swart said. “You recover from measles but you’ve lost part of your [immune-system] memory.”
He and others are now studying the immune-system response to measles in humans during outbreaks of the disease.
Write to Melanie Evans at Melanie.Evans@wsj.com and Betsy McKay at betsy.mckay@wsj.com
https://www.wsj.com/articles/measles-cases-continue-to-soar-stirring-concern-over-long-term-effects-11555337326
2019-04-15 14:23:00Z
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