In the movie CONTAGION, what was Dr. Ally Hextall's position?

One of my favorite movies, which has actually inspired me to think about entering the medical field, specifically epidemiology or pathology. I was wondering though, and I have wondered for a while now, what was Dr. Ally Hextall's doctorate in? Was she an epidemiologist or what? It seems she spent most of her time in BioSafety Level 4 labs, so I take it she may be an epidemiologist. Remember, Dr. Hextall portrayed by Jennifer Ehle and she is the one who worked alongside Dr. Ellis Cheever to create a vaccination for Meningoencephalitis Virus-1 If anyone can pinpoint exactly what she is would be extremely helpful, as I wish to look into studying to be whatever type of doctor she portrayed...