19. Public Health Infectious Disease – Dr. Troy Grennan

Dr. Troy Grennan

“Infectious diseases is… detective work… Really trying to figure out undifferentiated problems… [People] don’t come in with a bug stuck on their face–you don’t know exactly what is going on, so you do have to do a lot of figuring it out.

Dr Troy Grennan pitching infectious disease subspecialty

  1. Profile:
    • Positions: Physician Lead (provincial HIV/STI program at British Columbia Center for Disease Control); Clinical Assistant Professor (Division of Infectious Diseases, University of British Columbia); Co-Principal Investigator (CIHR team grant for HPV screening and vaccine evaluation in HIV-positive men who have sex with men)
    • Training: Infectious Disease and Medical Microbiology Training (McMaster); Internal Medicine Residency (Toronto); MD (McMaster)
  2. Pitch: Very broad specialty dealing with diagnosis, management, and prevention of many diseases; can tailor and focus job to your interests.
  3. Path: He was interested in many specialties in medical school but decided on internal medicine and infectious disease subspecialty due to complex cases and interest in HIV care; he took a long time to decide his life but currently works in clinical and public health role at provincial health services agency.
  4. Personal: He loves collaborative work and care and tries to be a better doctor to answer patients’ increasingly informed questions.
  5. Philosophy: Keep an open mind, it’s ok to not know, and don’t be afraid to do extra work – it may be useful later!

Elevator Pitch


  • “Lots of people do general infectious diseases but also people do very specific work many people have never heard of”
  • Infectious disease (ID) specialty is quite broad and deals with diagnosis, assessment, management, and prevention of variety of diseases
  • Bulk of job is detective work to figure out undifferentiated problems
  • Can tailor and focus work to your interests



  • He does a lot of non-standard work in sexual health and needs to be very open about many things people find uncomfortable, weird, difficult to talk about but also must approach with non-judgmental mind (sex-positive approach)
  • Many people think ID doctors are cerebral, OCD, detail oriented, stuffy but he’s actually pretty laid back!

Stereotypes of Infectious Disease


  • 3 main detractors for US internal medicine residents’ decision to pursue fellowship in infectious disease are salary, desire to be a generalist, and limited job availability
  • Dr. Grennan’s response:
    • Generalist: it’s a tradeoff and everyone struggles with decision to be generalist vs. specialist
      • Lot of mundane stuff in any specialty and weird cases are rare
      • You just have to decide what you want to do
    • Jobs: competitiveness of training programs and job market vary every year, often harder to get jobs at large academic centers like Toronto but easier in community hospitals and satellite sites
      • Good thing about doing any specialty in internal medicine is that there are always jobs available for internists
      • Internists in US do a lot of primary care and family med-based stuff so big  difference from Canada
    • Salary: ID isn’t procedures based so probably won’t make millions but don’t find too many people choosing specialty based on salary in Canada
      • “do what you love, don’t worry about the money or jobs”

Referenced Material: Bonura et al. Factors influencing internal medicine resident choice of infectious diseases or other specialties: a national cross-sectional study. Clinical Infectious Diseases 2016;63(2):155–63.



Medical School

  • Mom says he took too long to figure out his life!
  • He wanted to be a doctor as a kid (think Fisher Price stethoscopes!) but in undergrad thought he wanted to do public health research with some clinical work for street cred
  • He then did a two-year second entry nursing program at U of T before deciding to go for medicine
  • He was always interested in HIV care, especially after doing some palliative care and work in West Africa on a research project
  • When he entered med school, he was really interested in infectious disease (he front loaded all of the rotations he was interested in during clerkship, then did electives and non-contenders at the end)
    • OB-GYN was his last rotation but he loved it! (lot of medicine but also procedure-based work)
  • Two main contenders were internal med and family med, he applied to both
    • HIV care is often done by specialized primary care (family med) physicians
    • He didn’t consider public health because he didn’t know that much about it (can also do family med with extra training in public health)
    • He ultimately chose internal medicine because he wanted to deal with more complex matters
  • You generally don’t get a good sense of many specialties in med school, especially for surgery (med students tend to be pushed to the back)
    • “Ok to not know and explore and be open to having your mind changed”

Residency and Beyond

  • He did some work in HIV clinic while trying to find research project for clinical epidemiology masters
  • He did diploma in tropical medicine and hygiene training in Peru (ID fellowship was helpful but not a required prerequisite)
  • He ended up adding on a year for medical microbiology technique (cool bacteriology, parasitology, and lab techniques)
    • You can’t divorce clinical work from lab work (microbiology diagnostics training turned out to be helpful during current COVID testing work as well!)
    • “Don’t be dissuaded from doing things that seem like extra work”, can still be useful experiences even if not directly relevant!
  • He completed CIHR Canadian Trials Network post-doctoral fellowship examining HPV in HIV-positive men who have sex with men (MSM)


  • You usually have to do research in med school and residency in any specialty to some extent
  • In academic medicine, need to work in education or research streams for promotions
  • Research is an expectation but not formal part of his job (he has to find time for it)
    • He currently does research because he’s interested (likes addressing innovative and impactful issues, e.g. novel methods for STI prevention)

Day-to-Day Life


  • Lots of meetings as a clinician working in public health
  • Clinical work one or two half-days a week – anal cancer screening clinic in surgical outpatient department at St. Paul’s Hospital in Vancouver
    • Assess people for pre-cancers, do high-resolution anoscopy
  • STI work in BC Centre for Disease Control – oversee other doctors in running of program from guidelines to clinical workflows, HIV pre-exposure prophylaxis clinics
    • A lot of time spent with trainees and research coordinator to ensure smooth running of program
  • Every two months, he goes to Yukon for one week of ID clinics
    • No other ID specialist in Yukon
    • Mostly HIV/Hep B/Hep C work
  • Call in general ID, hours can vary
    • Hours can be long in hospital but home calls are much better
    • He currently does call for public health role for province (all phone based once every quarter)
    • Also some phone-based home calls as part of infection control work for current COVID redeployment
  • He loves multidisciplinary approach to care and work
    • Work with expert nurses to integrate services, very collaborative and non-hierarchical
    • “Much more pleasurable to come to work when you love the people around you”
  • Patients are increasingly less likely to accept things at face value and often question him, so he’s forced to be more humble and justify what he does (makes him try to be better)

Public health: Lot of people struggle to understand his job but basically he works in a provincial health services authority that also does clinical work (sexual health, TB clinic, physician leads)

Final Comments


  1. There’s flexibility within any specialty to do less obvious things that usually don’t fall within that specialty.
  2. Keep an open mind during training, try to get breadth of experiences that aren’t all focused on what you think you’re interested in – remember you’re making decisions without all of the information
  3. Travel a lot and get a dog!