Measles cases continue to skyrocket, a source of concern for long-term effects

The increase in the number of cases means 2019 may soon become the worst case of measles in the United States since the official elimination of the disease – that is, it stopped circulating – in 2000. 2014, the worst year since elimination, 667 cases were reported.

This year's US outbreaks are among the latest in developed countries, where high overall immunization rates and access to health care make measles mortality uncommon. Measles complications and deaths pose a greater threat in the poorest regions of the world, where inadequate nutrition and increased exposure to other infections can make it more difficult to control the effects of measles .

The virus continues to awaken in the United States among groups with low vaccination rates, often after exposure to overseas travelers returning with the disease. An epidemic of Orthodox Jews in New York this year has led to an increase in the number of cases in the United States. Health officials in New York City said Friday that there had been 285 cases of measles in the city and that more than 11,000 people had been exposed to the virus.

Researchers studying the virus claim that the anxiety generated by these outbreaks extends beyond the effects of the initial infection and has long-term consequences for the health of the victims.

The virus could leave the immune system in a temporary state of amnesia, leaving the immune system uncontrollable and effectively attacking some of the invaders it had seen before, according to recent research. The memory loss of the immune system could leave the body subject to more serious infections for two to three years, until it learns from a hard-earned experience, to repel the aggressors , researchers said.

"You do not have that quick response," said Michael Mina, an assistant professor at Harvard University, who studies the immune system's response to the virus. "You have to create it from scratch again."

Measles is highly contagious and affects up to 90% of sensitive people. 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, although rare, are serious: about one in 1,000 people in the United States with measles contract encephalitis, or inflammation of the brain, which can develop a week or two after the onset of symptoms. a rash and leave the victim deaf or suffering from an intellectual disability.

Measles can also lead to another serious complication: subacute sclerosing panencephalitis, a rare central nervous system disease that is usually fatal. It usually occurs seven to ten years after a person with measles.

"We can not tell you if your child is going to get well or not well with measles," said Thomas Clark, deputy director of the CDC's Viral Diseases Division. "That's why we vaccinate all children."

Research on immune system amnesia, though under development, could help explain evidence suggesting that measles immunization helps reduce the risk of other infections, said experts in public health and public health. in infectious diseases. World Health Organization advisers have found that studies, although largely focused on observation, indicate such a benefit, they said in 2014.

Measles mortality rates have dropped with vaccination. Nevertheless, the number of deaths worldwide could be higher than that recorded if the virus created amnesia in the immune system for a prolonged period and exposed the body to a risk of more serious infections by other agents pathogens, researchers said.

A 2015 study that suggested long-term damage to the immune system looked closely at child mortality rates before and after the arrival of measles vaccines in the United States, Denmark, England, and Wales.

Before widespread vaccination, the researchers found that the incidence of measles was a predictor of infant mortality from other infectious diseases in the next 28 months to 35 months, said Dr. Mina. one of the authors of the study. "It's like a shadow."

According to the study published in the journal Science, when vaccination has helped reduce the incidence of measles, child deaths due to other infectious diseases have also dropped.

Improving health care in the United States would probably now prevent these deaths, Dr. Mina said. However, a separate study conducted between 1990 and 2014 on children aged 1 to 15 years in the United Kingdom showed that children who were recovering from measles also risked being diagnosed with subsequent infections and infections. need prescription drugs.

The results of the study suggest that the cost of measles outbreaks may be greater than public health investments to contain the disease. By the end of March, public health expenditures incurred by Washington State to contain an epidemic that had infected 74 people by April 10 totaled more than a million dollars, said Dr. Scott Lindquist, communicable disease epidemiologist at the Washington State Department of Health.

Pediatricians and US public health officials said the research did not change the way they monitored measles patients. Pediatricians should already be closely monitoring children who contract measles as a result of additional complications, said Sean O'Leary, a pediatric infectious disease specialist who contributes to the drafting of practice recommendations for the American Academy of Pediatrics.

"Measles is a very serious disease in many ways, and that's one of the ways," he said about the complications that followed.

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 enter the cells by finding unique receptors or cell docks that they can exploit. Measles specifically target receptors on cells of the immune system, including memory cells reminiscent of previous infections so that the body's defenses can respond more effectively. The virus kills these cells during its propagation. Meanwhile, other immune system cells attack the memory cells that harbor the virus to stop the infection.

The exhausted immune system memory cells could leave the body unable to remember and react forcefully to invaders already seen, said Rik de Swart, a virologist at Erasmus MC, University Medical Center of Rotterdam in the Netherlands, whose research has illuminated the process in monkeys using fluorescent cells. "It eliminates measles," said Dr. de Swart. "You recover measles but you have lost some of your [immune-system] Memory."

He and others are now studying the immune system 's response to measles in humans during outbreaks of the disease.

Write to Melanie Evans at [email protected] and Betsy McKay at [email protected]