An ongoing dialogue on HIV/AIDS, infectious diseases,
May 7th, 2009
Human Rabies from Bats: Another Look at the Numbers
The gang from Canada is at it again, reviewing human rabies cases from bats and trying to make some sense of the data.
(For a summary of their outstanding prior paper in CID, read this.)
But before we get to their latest masterwork, here are some questions to ponder. While doing so, keep in mind the practice of giving the rabies vaccine to a person with “bedroom exposure to a bat while sleeping, without evidence of direct physical contact”:
- Are you more motivated by avoiding an “error of omission” (a mistake from not doing anything) than an “error of commission” (a mistake from doing something)?
- Do you ever envision yourself being named in a lawsuit for failure to provide preventive therapy?
- Do you sometimes imagine yourself cited in a newspaper as the doctor who said, “that isn’t necessary”, only then to have the patient in question be the one in a zillion who gets rabies? (“We called Dr. Freepner, and he said not to do it. Later, she was dead.”)
- Do you feel you have a moral imperative to provide preventive therapy for a condition that will likely be fatal, no matter how unlikely it is that a patient will develop it?
- Do you think cost, limited supply, and personnel issues should always be secondary considerations when making decisions about an individual?
- When you read official guidelines that state that preventive vaccination “can be considered” in low but not zero risk circumstances, do you interpret that to mean it should be given?
- Did you ever find yourself doing something clinically that you just knew made no sense, yet you did it anyway?
I suspect we all could answer “yes” to some, if not all, of the above questions. These are not rational decisions, they are emotional ones.
Hence this latest paper is such a joy to read. It provides yet more evidence that a policy of giving the rabies vaccine to patients with a “bedroom bat exposure” but no contact is, to be blunt, pretty ridiculous. Some of the key numbers:
- Based on a telephone survey done in Quebec, fewer than 5% of people with such bat exposure get vaccinated.
- The estimated incidence of rabies due to this exposure is 1 case per 2.7 billion person-years.
- The number needed to treat to prevent a single case of human rabies from bedroom exposure (but no contact) is around 2.7 million.
- If all potential exposures were investigated and evaluated fully — after all, this is recommended in the guidelines, right? — this would require 49 physicians, 491 nurses, and 259 veterinarians working full-time for a full-year. And this estimate does not even include administration of the rabies vaccine!
In short, what we are doing is absurd — we are giving preventive therapy to a small proportion of the potentially exposed only because they show up, and because we can. It has very little to do with preventing actual cases of rabies, but it sure makes us and our patients feel better.
But if it’s indicated for those who show up, what about the 95% who don’t? Solid quote:
Failure to intensely pursue a greater proportion of eligible persons then becomes paradoxical public policy: a recommendation that is known to be sustainable only if ignored by most eligible persons is of doubtful usefulness and questionable ethics.
So what are we to do? The authors conclude that the recommendations for rabies vaccine for bedroom or other occult exposures “be reconsidered.” I read that to mean, “be scrapped.”
And someone please point me in the direction of why some irrational physician behavior is so hard to shake.