On any given day, more than 4,000 people pass through the library at California State University, Los Angeles.
On April 11, one of them had measles. The building has only one entrance, which means that anyone who entered or exited the library within two hours of that person's visit potentially was exposed to one of the most contagious diseases on Earth.
It's the stuff of public health nightmares: Everyone at the library between 11 a.m. and 3 p.m. that day had to be identified, warned and possibly quarantined. Measles is so contagious that up to 90% of people close to an infected person who are not protected by a vaccine or previous case of the disease will become infected. But how could the university figure out who had been in the library during that time frame? And which of those people were vulnerable to infection?
Rooting out answers to such questions is the job of the public health detectives who work at health departments across the country.
In 2000, the United States declared the measles eradicated, thanks to widespread use of vaccines. But the virulent disease is back, with more than 1,000 cases confirmed nationwide this year through June 3 -- the greatest number since 1992. For every thousand cases, 1 to 3 people with measles will die, even with the best of care, according to the Centers for Disease Control and Prevention. So public health departments are redirecting scarce resources to try to control the spread.
Using basic techniques in place for over 100 years, public health investigators work to control an outbreak before it balloons. Such investigations have evolved with new technologies but remain among the best defenses against infectious disease outbreaks -- and among the great untold costs of an epidemic.
The New York City Department of Health and Mental Hygiene, which has confirmed 566 measles cases since September, has spent more than $2.3 million on related investigations. The Los Angeles County Department of Public Health estimates spending as much as $2,000 to track down each contact of a confirmed patient -- and it has made hundreds of such efforts in recent months.
"Public health departments across the country have had their budgets tightened in a sustained fashion over the past 15 years," said Dr. William Schaffner, an infectious-disease specialist at Vanderbilt University. "There are no public health departments that are like firemen playing pinochle and waiting for an outbreak. They have other things to do, and they have to put aside those tasks to deal with an outbreak."
At Cal State LA, public health officials visited the library and tried to figure out 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 which library employees were present. They scoured library records to find anyone who had checked out books or logged onto a library computer during the specified time period.
But they realized they were missing others who may have come in to browse, work or eat at a library cafe. So, school officials sent out emails and posted on Facebook, Twitter and Instagram to ask anyone who may have been at the library to come forward.