In God we trust. Everybody else needs data. - Rick Peterson

Friday, July 02, 2004


Investigating the Yankees

Both Jason Giambi and Kevin Brown of the Yankees have intestinal parasites. Although the specific parasites are not described, they most likely both have Giardia infections.

Giardia has a fecal-oral transmission route. The transmission route responsible for the most cases is contaminated water supply, but that is far from the only exposure. Transmission can occur in any route by which with poor sanitation practices can lead to ingestion of fecal material.

When the news came out about Giambi, I drafted a post about it that I decided not to publish, but now that Brown has also reported an infection, it's worthy of more attention.

With both Brown and Giambi becoming symptomatic about the same time and having many shared life elements, they very likely have a common exposure. Giardia has about a one to two week latency period. If Giambi and Brown both first showed symptoms recently, attention should be focusing on the first half of the Yankees recent road trip to Arizona, Los Angeles, and Baltimore, including the off-day on June 21. In the Newsday story I linked to above, though, Brown suspects the exposure may have occurred during the season-opening trip to Japan. Brown says his symptoms started the about 3-1/2 weeks after the return from Japan; if so, that would make Japan less likely as the place where he picked up the infection. The Yankees team doc also discounts exposure in the Japan trip, though he tries to do so simply on the basis that Japan is a developed country with advanced sanitation practices. That's poor logic, as Giardia outbreaks occur in all countries. The timing of the onset of symptoms is much more definitive. The onset of diarrhea and flatulence is more significant than simple weight loss.

The Yankees will probably survey the rest of the team to see if other team members are infected, but that there likely will be no further investigation by anyone else, even though Giambi and Brown are high profile individuals. Normally high profile cases receive disproportionate attention and interest, and it's easier for public health investigators to receive support for detailed investigations in high profile cases. In the current situation, though, credible suspicions have not been directed at any particular person or location, so there's little incentive for any public health organizations to initiate an investigation. So the Yankees doc will treat Giambi, Brown, and any other cases they find, and that will be the end of the issue. Were a more detailed investigation to be conducted, it would likely proceed somewhat as described below.

The possibility that Giambi and Brown were sex partners would probably be eliminated quickly (though a responsible epidemiologic investigator will address the issue discreetly and carefully). A contaminated public water supply system is not likely, since there would be reports of many more illnesses than just Giambi and Brown. Specifically, if a public water supply system were contaminated, a large population would have been exposed. If the exposure were sufficient to infect two healthy males in top physical condition, people in the exposed population who are in poor physical condition or who have weakened immune systems should also be showing symptoms. In a case such as this, investigators would immediately survey morbidity data for the elderly and AIDS cases, as these are the population segments where the infection rates will be the highest and most severe.

In the Newsday article, Brown says that he and Giambi don't hang together outside the team, so the two of them probably would not show common exposures from having gone hiking or rafting together on an off day. They are also not likely to have common exposure from having being involved with changing and diapering of the same infants or in the same physical setting (i.e., at someone's house).

With that background, ingestion of contaminated food or beverage would be the exposure most intensively scrutinized. Investigators would look at all situations where Brown and Giambi ate food prepared from the same kitchen, particularly if they ordered the same items off of the menu. They would look closely at consumption of fresh and uncooked fruits and vegetables, and of any meats that were not fully cooked. They would also examine post-preparation food handling at suspect locales. This would include food handling procedures, as well as identifying specific food handlers who may have had contact with food items served to both Giambi and Brown.

After identifying common elements, the investigators would look for other individuals, not associated with the Yankees, who may share that exposure. For example, they would contact other customers at restaurants who might have ordered the same dishes. If Giambi and Brown both retrieved ice from the same ice machine in a hotel, they might track down other guests who stayed on the same floor of the hotel who might also have taken ice from the same ice machine. If the investigators are then able to identify other individuals who became sick and who share the common exposure route, that would be virtually conclusive proof of the source and mode of transmission.

Background note: the early part of my career was spent in public health engineering pertaining to water supply, and I have provided engineering technical support for investigations of water supply as a potential source of Giardia transmission.

[Note: the fifth paragraph of this post has been edited. The original post said followup investigation was likely, but after further reflection and some correspondence with Will Carroll, I don't think that's likely to occur.]

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