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Creative Minds: Does Human Immunity Change with the Seasons?

Posted on by Dr. Francis Collins

Micaela Martinez

Micaela Martinez

It’s an inescapable conclusion from the book of Ecclesiastes that’s become part of popular culture thanks to folk legends Pete Seeger and The Byrds: “To everything (turn, turn, turn), there is a season.” That’s certainly true of viral outbreaks, from the flu-causing influenza virus peaking each year in the winter to polio outbreaks often rising in the summer. What fascinates Micaela Martinez is, while those seasonal patterns of infection have been recognized for decades, nobody really knows why they occur.

Martinez, an infectious disease ecologist at Princeton University, Princeton, NJ, thinks colder weather conditions and the tendency for humans to stay together indoors in winter surely play a role. But she also thinks an important part of the answer might be found in a place most hadn’t thought to look: seasonal changes in the human immune system. Martinez recently received an NIH Director’s 2016 Early Independence Award to explore fluctuations in the body’s biological rhythms over the course of the year and their potential influence on our health.

Martinez has teamed with researchers at the University of Surrey, England, who specialize in the study of biological rhythms, including sleep. With the help of their state-of-the-art facility, Martinez will study 12 people during each of the four seasons. During each visit, study participants will spend three days in the lab under carefully controlled conditions. Using a specially-designed catheter, Martinez will collect blood samples each hour, even while participants are asleep. With those blood samples in hand, Martinez will look for telltale changes in hormone levels, gene expression, and immune activity that predictably follow with the seasons.

To complement this work, Martinez will track possible seasonal outbreaks involving shingles, the painful viral infection in the nerves of the skin that strikes many older adults. Shingles is caused by the varicella-zoster virus, the same herpes virus that causes chickenpox. Varicella-zoster virus remains dormant for years in the spinal and cranial nerve roots in people who have had chickenpox, and preliminary research suggests that it may tend to reactivate in the spring to cause shingles.

Specifically, Martinez will analyze California hospitalization data for herpes virus infections (chickenpox, shingles, herpes simplex, and cytomegalovirus) spanning the last three decades. She hopes the data will allow her to estimate the transmission and reactivation rates of the various viruses and make recommendations about the optimal timing for administering vaccines.

Martinez is clearly at the beginning of an intriguing scientific journey. But she surely didn’t follow a direct path to get there. When she was a child, her father was incarcerated. With things unsettled at home, Martinez bounced from school to school and landed in an alternative high school for low-performing students. Then after high school, Martinez considered the military but opted for community college in Colorado. Her goal: get a two-year associate degree and become an emergency medical technician (EMT).

That’s when her life took a sharp and remarkable turn. While taking a required algebra class—her first math class since her sophomore year of high school—Martinez kept acing her exams. Realizing she had a gift for math, her confidence and self-esteem soared.

Fortunately, her community college professors recognized her potential and recommended her for the Bridges to the Baccalaureate Program, supported by NIH’s National Institute of General Medical Sciences and designed to increase the number of community college students who go on to research careers in the biomedical sciences. She transferred to Colorado State University, Pueblo, and then on to the University of Alaska Southeast, Juneau, where she majored in biology and math. In 2015, Martinez received her Ph.D. at the University of Michigan, Ann Arbor, in applied mathematics and infectious disease ecology.

While most would consider her difficult childhood experiences as a major impediment, Martinez doesn’t. She says it’s actually given her a sense of freedom. “One really good thing about the background I come from is that I’m never really scared to fail,” she says. “I’ve already won.” May she keep on winning—to help all of us at risk for seasonal viruses!


Martinez Lab (Princeton University, Princeton, NJ)

Martinez NIH Project Information (NIH RePORTER)

NIH Director’s Early Independence Award (Common Fund)

NIH Support: Common Fund

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