Measles History 101: What is the severity of this year's measles outbreak? : Coups

In 2000, the Pan American Health Organization announced a monumental achievement in public health: extensive immunization efforts, overseen by the Centers for Disease Control and Prevention, had effectively eliminated measles in the United States .

The disease, which affected between 3 and 4 million people each year in the United States prior to the time of vaccination, was now isolated with small controlled homes related to international travel.

The epidemic of this year's records threatens this achievement.

Since January, more than 700 cases of measles have been reported in 22 states. Most of those affected have never been vaccinated. Sixty people have been hospitalized and the number of cases continues to increase, although in some areas, such as the Pacific Northwest, epidemics have blurred.

René Najera, epidemiologist and editor of the History of Vaccines website, says that while current figures are minimal compared to the number of cases recorded in the first half of the 20th century, they still make sense.

"We are about to tip in. If business continues to climb, the US could lose its elimination status," Najera said.

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A disease is considered to be eliminated from a country when it can no longer be contracted within its borders, although cases related to international travel – such as those occurring since 2000 – may still be happen.

Losing elimination status would be a failure of one of the greatest achievements of our history in public health.

Prior to the 1960s, "Measles was basically a universal childhood experience," says James Colgrove, a public health historian at Columbia University.

Essentially, everyone got it. Of the millions of people infected each year, 400 to 500 would die, tens of thousands would be hospitalized and hundreds would face serious complications, such as encephalitis, according to the CDC.

"People had suffered the harmful effects of measles and were therefore receptive to the vaccine as soon as it was published," Najera said.

The first steps towards a measles vaccine were made in 1954, when John F. Enders and Dr. Thomas C. Pebbles collected throat swabs and blood samples from children at a Boston school that had recently epidemic.

Enders and his lab managed to isolate and grow the measles virus, and then adapt it to chicken embryos, which eventually resulted in the release of a vaccine in 1963. In 1968, Mauritius Hilleman and his colleagues have developed a more effective vaccine. same measles vaccine (associated with a vaccine against mumps and rubella) used in the United States today.

"The measles vaccine has been widely accepted and well received," said Najera. Between 1964 and 1974, the number of measles cases in the United States decreased. Meanwhile, states have begun passing laws requiring proof of immunization in order to enroll in public schools. "This type of legislation has contributed to vaccination efforts," said Colgrove.

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In 1978, vaccination efforts had worked so well that the CDC set a goal of eliminating measles from the United States in 1982. Amesh Adalja, a physician and infectious disease specialist at Johns Hopkins University, explains that to be eliminated, a "collective immunity" is needed. or a level of immunity within a population such that the chances of vulnerable people (such as infants or immunocompromised people) getting the virus are extremely low.

"Measles is one of the most contagious infectious diseases, which means you need more than 93% immunity to protect a population," Adalja said. "One dose of vaccine has proven to be insufficient."

In 1989, measles reached 18,193 cases, of which about 40% occurred in vaccinated children. After this outbreak, public health officials began recommending two doses of measles vaccine. This recommendation, coupled with increased efforts to vaccinate low-income communities, has worked. Measles rates continued to fall, allowing the Pan American Health Organization to declare the disease eliminated from the United States in 2000.

"It has been a huge success in public health, especially because measles is so contagious," said Colgrove.

Of course, since then, outbreaks of measles have occurred, but all result from international travel. In 2014, 383 cases were reported in the Amish community of Ohio, where vaccination rates are low. Two Amish men have returned from the Philippines after being rescued by the typhoon. In 2015, a home appeared in Disneyland, where 147 cases were reported to have been caused by a traveler from the Philippines.

Since the elimination was declared, all the epidemics eventually died out, the virus hitting the wall of herd immunity, leaving intact the elimination status of the United States.

But now, public health officials fear that the elimination status is disappearing as measles returns. "If things do not change, we could end up in the United States where measles is not eliminated," Najera said.

This would not mean that the United States would return to have 3 to 4 million people affected each year; vaccination levels are high enough to prevent this. But epidemics would become more common.

Unvaccinated young children have the highest risk of contracting measles and developing rare but serious complications of the disease.

"Statistically, once we have exceeded 1,000 cases of measles, we will die," said Najera. "For an entirely preventable disease, it is unacceptable."

"We are not there yet, but we are getting closer," Najera said. "If these numbers continue to increase and new cases do not appear associated with trips abroad, we are here."

Most cases of the current outbreak are travel-related, but according to Mr. Adalja, the longer the outbreak, the more difficult it is to trace any case to an introduction by a traveler. While the epidemic is rife, the concern is that the national measles reservoir is expanding, which increases the likelihood that vulnerable people will contract the infection inside our home. borders.

The United States could reach this point in a few months, according to Adalja. "If these chains of epidemics continue to burn for a year, we would be able to question the status of elimination," he said. The cause? Refusal of vaccines.

"We had not been threatened with losing our elimination status until vaccination refusal rates increased," Adalja said. "Because of the inaction of some individuals, they let measles come back in. These are totally preventable outbreaks."

Statewide MMR coverage varies from 85% in Missouri to 98% in Massachusetts, according to 2017 data provided by the CDC. And some local communities have even lower rates.

Najera says that states and local governments should act now Many have already. On April 9, the New York City Health Commissioner ordered all unvaccinated persons living or working in Brooklyn to be vaccinated or face a $ 1,000 fine. On April 19, a judge confirmed the order. The Washington State legislature is currently considering legislation to remove personal exemptions for the measles, mumps and rubella vaccine.

"If we do everything in our power to vaccinate people, we could contain this epidemic," said Najera. "But we are not there yet."

"The 200-year history of vaccines has shown that it is always difficult to maintain high levels of immunity because any vaccination program will inevitably become a victim of its own success," said Colgrove. "The better vaccines work, the more people think they no longer need them."

Jonathan Lambert is an independent science journalist based in Washington, DC. You can follow him on twitter @ evolambert.