Catching a Disease
By Samantha B. Bonar '90 | Photo by Garrett Ellwood
Paul Mead ’81 M’83 is on the trail of a serial infector. As chief of epidemiology and surveillance activity at the Centers for Disease Control and Prevention’s National Center for Emerging and Zoonotic Infectious Diseases in Fort Collins, Colo., Mead is the Zika Response Team lead, which puts him directly on the front line of tracking this troubling virus in the United States.
“When Zika hit, many people were being called in to help, and I was one of those people,” Mead says. “Our division located here in Fort Collins, in addition to having responsibility for working on bacterial infections, also works on viral infections, like West Nile. So, it’s kind of our division’s pathogen.”
In particular, he’s been keeping his eye out for the first U.S. case of Zika infection that doesn’t involve travel or sexual transmission. That incidence emerged in Miami on July 29, when Florida Gov. Rick Scott announced the first four cases of locally acquired Zika in the United States (up to 30 cases as of press time). This game-changer means the virus has infected mosquitoes here, and many more Americans could potentially be at risk.
An ongoing Zika virus outbreak throughout Central and South America and the Caribbean began in Brazil in 2015. According to the World Health Organization, 31 countries and territories in the Americas are currently affected. Zika virus was first discovered in 1947 and is named after the Zika Forest in Uganda. In 1952, the first human cases of Zika were detected and since then, outbreaks of Zika have been reported in tropical Africa, Southeast Asia, and the Pacific Islands.
Zika, a flavivirus related to dengue, West Nile, and yellow fever, is spread mostly by the bite of an infected Aedes species mosquito. The illness is usually mild, with symptoms lasting up to a week, and many people experience no symptoms or only mild ones. Zika infection during pregnancy, however, can cause a birth defect of the brain called microcephaly and other severe fetal brain defects, according to the CDC.
On February 1, the World Health Organization declared a Public Health Emergency of International Concern because of clusters of microcephaly and other neurological disorders in some areas affected by Zika. A week later, the CDC elevated its response efforts to Level 1 activation, the highest response level at the agency, and enlisted hundreds of staffers to work on the crisis.
Although the number is growing rapidly, at press time there were nearly 2,000 cases of Zika infection in the United States—most in people who had traveled to Zika-affected areas and brought it back here, where some of them transmitted it sexually. These imported cases could result in local spread of the virus in some areas of the country, the CDC says, such as the new cases in Miami. There are another 6,500-plus cases in Puerto Rico, where mosquitos are carrying the virus.
Those same mosquitos are present in the United States, particularly in the Southeast and on the Eastern seaboard. “We give a lot of advice to people with Zika virus about how to prevent mosquito bites,” Mead says. It’s hard to speculate about what a Zika virus outbreak in America would look like, but he expects it would be similar to the chikungunya virus, which saw a limited outbreak domestically in 2014-15 when about eight to 12 cases stateside were thought to be locally acquired through mosquito bites.
“If that is the guide, we don’t necessarily expect a major catastrophe,” Mead notes. “All of that said, Zika virus has been quite surprising in many ways, including sexual transmission. I think public health officials are keeping our fingers crossed and hoping it will be very limited in scope, but we still need to be prepared to best respond to it to ensure that’s the case.”
Mead received his bachelor’s and master’s in biology at Oxy in 1981 and 1983, respectively, originally intending to be a research biologist. He particularly relishes his memories of summers spent conducting research with biology professor Marty Morton at Tioga Pass, the eastern entry into Yosemite National Park, collecting data about birds. “It brought opportunities to many students, including myself, to learn basic skills of field biology,” Mead says, adding that Morton “was exceptional in facilitating and encouraging people’s curiosity.”
“In many ways what I do now is not unlike that biologic research,” he adds. “I’m trying to understand basic principles about a disease or organisms—it’s just that it’s a little more applied in that I’m following it through on human populations.”
According to former roommate Timothy Chapman ’79, Mead kept busy pulling pranks when he wasn’t doing research as an undergrad. One time Mead scaled an outer library wall to hang a 10-foot-long papier mache pencil stub he’d made from the roof, while another time he convinced Chapman to climb one of the Patterson Field towers with him, “running all the way back to the dorm” when they got caught by Campus Safety. “He was a little more of a risk-taker than I was—all in the spirit of fun,” Chapman says. “At the base of all his work, all his effort, it’s just fun for him. He loves doing it. I think he’s managed to carve out a life that he really likes.”
After completing his M.D. in 1987 at the University of Colorado Health Sciences Center in Denver, Mead finished his residency in internal medicine in 1990 and served as an infectious diseases fellow at UC San Francisco for three years. In 1994 he received his master’s of public health from UC Berkeley. An infectious-disease physician by training, Mead joined the CDC in Atlanta that same year as a staff epidemiologist. He initially focused on foodborne illnesses, which he calls “terrifically interesting” and “rewarding from a public health standpoint because you can track it, identify it, and stop it.”
In 2000, Mead transferred to the CDC’s Emergency Operations Center in Fort Collins. Zoonotic (spread between animals and humans), vector-borne (transmitted by insects like mosquitos and ticks), and enteric (intestinal) diseases are his game. He led the government response to anthrax in 2001, H1N1 in 2009, and Ebola in 2014—and before getting distracted by Zika, he was chief of epidemiology and surveillance for Lyme disease, which infects an estimated 300,000 Americans each year.
The CDC is working with international public health partners and state and local health departments to alert healthcare pro-viders and the public about Zika; post travel notices and travel-related guidance; provide state health laboratories with diagnostic tests; and monitor and report cases of Zika, which will help improve understanding of how and where the virus is spreading.
That last area is where Mead steps in. It is his role to track where and how Zika is spreading in the United States. “In response to Zika, the CDC has activated its emergency response center in Atlanta and has brought together a variety of people,” Mead says. “I was volunteered to help out with the epidemiological aspects. The team deals with surveillance of cases and some of the analytics of some of the cases that go on—Zika as a cause of Guillain-Barre or microcephaly, for example.”
Most recently, Mead has been examining semen samples of men in the United States who have been infected with Zika to try to determine how the virus is being sexually transmitted—“which is quite unprecedented,” he says. “Other viruses have never really been known to be spread sexually, only through mosquitos, so it’s quite a remarkable difference. There’s a lot we don’t know about it, including how long men have it in their semen and if it is constantly there or if it kind of comes and goes.”
Leading up to the Summer Olympics, there was much debate about whether the games should be held in Rio de Janeiro, given the ongoing outbreak there. The CDC concluded that “for most countries and for the most part, the additional travel to Brazil is actually fairly minimal compared to existing travel,” Mead says. “Having the Olympics in an affected area does not substantially increase the number of people exposed to the virus, simply because a number of people go to those countries every day anyway.”
With statistical models showing a widespread outbreak in the United States unlikely, why has Zika got people so spooked? “I think probably it is just the uncertainly of it,” Mead says. “It’s clear there’s a great deal we don’t know about this virus. The trajectory about this epidemic is always a little difficult to anticipate. Whether it will become highly endemic in certain areas of the Americas or will sort of burn out and become rare, we don’t know. That uncertainty is troubling for everyone. And, obviously it has devastating short- and long-term consequences for individual patients—mostly for infants.”
Having spearheaded the CDC’s response to numerous public health crises, Mead offers this advice to those still frightened by Zika: “I think there are precautions people should be aware of, particularly pregnant women. We recommend that pregnant women not travel to affected areas because of potential consequences to the fetus. But in terms of sort of panic in the streets, hopefully that will not be the case. Panic is never particularly helpful in any circumstance.”
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