How measles detectives work to contain an epidemic

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Every day, more than 4,000 people pass through the California State University Library in Los Angeles.

On April 11, one of them had measles. The building has only one entrance, which means that anyone entering or leaving the library within two hours of their visit has been potentially exposed to one of the most contagious diseases on Earth.

This is the nightmare of public health: everyone in the library from 11h to 15h. that day was to be identified, notified and possibly quarantined. Measles is so contagious that almost 90% of people close to an infected person who are not protected by a vaccine or a previous case of the disease will be infected. But how did the university determine who was in the library during this period? And which of these people was vulnerable to infection?

The job of public health detectives working in the country's health departments is to find answers to these questions.

In 2000, the United States declared the eradication of measles, thanks to widespread use of vaccines. But the virulent disease is back, with more than 1,000 confirmed cases nationwide this year until June 3 – the highest number since 1992. And public health departments are redirecting scarce resources to try to control the propagation.

Using basic techniques that have been in place for more than 100 years, public health investigators focus on controlling an outbreak before it appears. Such surveys have evolved with new technologies but remain among the best defenses against epidemics of infectious diseases – and among the enormous costs of an epidemic.

The New York City Department of Health and Mental Health, which has confirmed 550 cases of measles since September, has spent more than $ 2.3 million on related investigations. The Los Angeles County Public Health Department estimates that it is planned to spend up to $ 2,000 to track every contact of a confirmed patient – and hundreds of these efforts have been made these last months.

"The budgets of public health ministries across the country have been steadily tightened over the last 15 years," said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University. "No public health service is like a firefighter playing pinochle and waiting for an epidemic. They have something else to do and they have to put aside these tasks to deal with an epidemic. "

At Cal State, public health officials went to the library and tried to determine exactly where the infected student had gone – the photocopy area, for example – to determine who might have been exposed. They worked with the school to identify the library employees present. They went through the library archives to find anyone who retrieved books or logged on to a library computer during the specified time period.

But they realized that they were missing other people who might have come to pick up, work or eat at a library cafe. So, school officials have sent emails and posted on Facebook, Twitter and Instagram to ask anyone who could be at the library to come forward.

Working together, health officials from the state of Cal and County drew up a list of 1,094 people exposed. All had to submit evidence that they had been vaccinated or that they had immunity.

During the investigation, 887 people were under quarantine order from the Los Angeles County Public Health Department until they could establish their immunity status.

Public health services routinely use this type of shoe leather detective work to monitor and control epidemics of sexually transmitted diseases and foodborne illnesses such as salmonella. But there is a palpable sense of frustration that distinguishes measles: it can be easily avoided.

"We should not have to use these old techniques. We should vaccinate everyone, "said Dr. Alan Melnick, director of public health for Clark County, Washington, who has registered 71 measles cases during a two-month epidemic that has occurred. finished in February. "That's what keeps me awake at night. If we stop vaccinating, we can return to the Middle Ages. "

During the Clark County outbreak, 237 people spent 19,071 hours on outreach activities, surveys and health surveillance for those at risk, costing more than $ 864,000. They investigated 53 exhibition sites, including 15 schools and the arena where Portland Trail Blazers play, across the Oregon state border. .

All of this work has resulted in delays in other programs, including health inspections in restaurants and a home visiting program for pregnant women and high-risk infants.

"It's not because the measles epidemic is raging that other communicable diseases are taking a vacation," Melnick said.

There was a time when public health officials would not have been disturbed. Prior to the end of the 19th century, officials "were busy controlling diseases like typhoid, cholera and smallpox," which had much higher mortality rates than measles, said Graham Mooney, associate professor at the University of Toronto. Johns Hopkins University, which studies the history of medicine. But with the decline of other infectious diseases, officials have become more focused on measles.

In the early 20th century, schools began to note which students had already contracted measles and who might be vulnerable. When a child gets sick, he can be sent home with a card to be signed by a doctor before his return. A school inspector often went to the house to ensure that the child remained isolated.

During an epidemic involving thousands of cases, authorities have warned in the newspapers and then on the radio, describing the likely symptoms and asking parents to keep their children sick at home. "Now it's Twitter; previously it was the Baltimore Sun, the Chicago Tribune or the L.A. Times. But the actual information may not have changed, "Mooney said.

Today, public health services are almost always informed of a case of measles through a health care provider. Measles is a reportable disease, which means that any provider who suspects a case must notify local health authorities. A service person visits the patient to conduct an interview and accurately determine where he might have gone while he is contagious. For measles, four days before rash and four days after, for a total of nine days.

The interviews are rigorous. "We need to evaluate their meeting places, their friends, their hobbies, what grocery store are they going to, take Lyft or Uber?" Explained Adarsh Almalvez, A.A. County Public Health Nurse.

For most people, it's hard to remember all the places they've spent days earlier. Some patients are reluctant to share details. Almalvez said that she started by making a report, asking them what their favorite foods were and where they had their hair cut. She said it was essential to call the patient.

She looks for clues around the house that could tell her who else could live there. Additional pairs of shoes in the hallway, for example, may indicate other residents. If she questions a woman and finds the toilet seat, she knows that a man probably went there too.

The goal is to go out with a list of all possible contacts and places that the patient has visited while being contagious. The results can be read as a strangely intimate window on a person's day. L.A. County recently released a patient itinerary in April; In an enviable day, this patient visited the Peet Cafe, Fratelli Coffee, TART Restaurant, The Grove, Los Angeles Farmer's Market, Whole Foods and La Brea's Tar Pits.

Public health officials visit each site to gather more information. They turn to carpooling services to locate drivers and other passengers who may have been in the same vehicle during the infectious period. In restaurants, employees are easily identifiable, but customers can be hard to find. Managers do not routinely watch video surveillance and do not search for people through credit card receipts. Instead, they rely primarily on press releases and social media to get the message across. They are also turning to schools and businesses to raise awareness.

This can be a lot of work, especially for medical clinics where a patient with measles initially sought care. During a 2017 outbreak, Children's Minnesota, a sister city hospital system, spent $ 300,000 on emergency response. Part of that was finding everyone in the waiting room within two hours of a patient with measles.

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