Measles does lasting damage that outlives the fever and the rash: the virus erases part of the immune system’s memory, leaving survivors vulnerable to other infections for as long as five years, researchers warned this week.
The warning carries new weight in the United States, where more than 6,000 measles infections have been recorded in less than two years and one Pennsylvania outbreak alone has produced 943 cases.
The condition is called immune amnesia, and it occurs to some degree in every measles infection, said Dr. Michael J. Mina, an immunologist and a co-author of two studies in the journal Science that established the effect. ‘The rash and the fever, that’s the tip of the iceberg,’ he told CIDRAP News. ‘The majority of the damage being done is under the surface.’
The measles virus exploits the immune system’s memory cells, using them to make copies of itself before destroying them, Dr. Mina said. Those cells carry the body’s memory of earlier infections. Without them, people lose protection they once held against bacteria and viruses, whether it came through infection or vaccination.
‘We will see thousands of additional medical clinic visits,’ said Dr. Mina, who is the chief medical officer of Invivyd, a biotechnology company developing experimental treatments for measles. ‘If your child gets measles, you have to be looking over your shoulder’ for years.
A child whose immune system forgets the common cold may simply catch last year’s respiratory viruses twice. But a baby who loses the protection of the pertussis vaccine could land in the hospital, and an adult who loses immunity to chickenpox, a far more severe illness in grown-ups than in children, could develop pneumonia, he said.
The risks run highest for children who were already sick or malnourished when they caught measles, said Dr. Boghuma Titanji, an infectious disease specialist at the Emory University School of Medicine, who treated children with the condition in Cameroon. In West Africa, she said, measles survivors were more likely to come down with malaria. ‘In general, they were just more sickly children.’
The effect is not confined to poor countries. Studies in Germany, Israel, Switzerland and Britain found that children who had measles were later more likely than others to need antibiotics or visit the doctor. ‘Immune amnesia is probably something that we’re going to encounter’ in the United States, said Dr. C. Mary Healy, an infectious disease specialist at Texas Children’s Hospital. ‘We’re on the cusp of finding out just how significant immune problems may be.’
Almost no one makes the connection, said Dr. Pia Pannaraj, vice chair of the American Academy of Pediatrics’ Committee on Infectious Diseases, who has treated measles patients in the United States, Asia and Africa. ‘People get measles, and then afterwards they will have recurrent ear infections or pneumonia, but they don’t tie it back to measles,’ she said. Even doctors often miss it; scientists have begun to understand the condition only in the past 15 years, and most physicians learned little about it in training.
Crystal Webster made none of those connections either. When she moved to Switzerland in 2008, at 27, she did not know the country was in its largest measles outbreak in years. Like most people born in the 1980s, Ms. Webster, now 44, had received a single dose of measles vaccine as a baby, the standard at the time. One dose of the measles, mumps and rubella vaccine prevents 93 percent of infections; two doses prevent 97 percent.
‘I remember lying on the wood floor, completely naked, spread eagled, because I didn’t want any part of my body to touch any other part of my body,’ she said of the painful rash that covered her in pustules during a hot summer, in a home with no air conditioning. The following winter, ‘I felt like I always had a runny nose,’ she said, blaming the unfamiliar germs of a new country. Her respiratory infections after measles are ‘certainly consistent with what we know about this phenomenon,’ Dr. Titanji said, though no one can say for certain what caused them.
A few years later, back in the United States, Ms. Webster developed shingles, a reactivation of the chickenpox virus, which can hide in nerve cells for decades. ‘I wrapped my stomach in gauze so that my pants wouldn’t rub up against the blisters,’ she said. Dr. Mina said her measles infection very likely ‘deleted or drained a portion of her antibodies against varicella,’ leaving her open to an early case of shingles.
Older Americans remember an era when nearly every child caught measles. Suzanne, a 71-year-old human resources consultant in Fort Myers, Fla., who asked to be identified by her first name to protect her privacy, fell critically ill at 6, two years before the measles vaccine arrived. Her sister confirmed her account. ‘My parents said I was on the verge of being hospitalized when my fever broke,’ she said.
Dr. Pannaraj belongs to the Measles Collaborative, a newly formed coalition of health care providers and public health experts working on measles prevention and education. The people catching measles now, she said, ‘tend to be those that are unvaccinated and may not interact with the medical system very often.’
‘I was pretty young to have all these things,’ Ms. Webster said. ‘I thought I had done what I needed to do to be healthy.’