The aspect of the recent Listeria monocytogenes outbreak that is likely to have the biggest impact on pathogen transmission litigation going forward is the ability to identify victims who acquired the infection years before the outbreak was finally recognized and the source identified. Thanks to the fact that in recent years some state health departments have begun preserving samples from patients diagnosed with certain infectious diseases the CDC  has realized, now armed with the ability to use of PFGE to “fingerprint” bacteria, that though the ice cream contamination wasn’t suspected until January of this year and wasn’t confirmed until last month people have been getting sick from it since as far back as 2010.

L. monocytogenes infections are acknowledged to be far more widespread than what’s reflected in the CDC outbreak statistics. Most cases produce nothing more than short term, mild, flu-like symptoms and go undetected as patients rarely get to a physician before they’re feeling better and so diagnostic tests aren’t even run. In the very old, the very young and the immune-compromised however it can produce a systemic or invasive infection with a significant mortality rate. It is these cases, assuming the infection is detected and it’s estimated that at least 50% of all such cases are accurately diagnosed, that get the attention of state health departments and the CDC. The silent tragedies are the miscarriages and stillbirths caused by L. monocytogenes. Expectant mothers can acquire the infection and experience nothing other than the vaguest sense of being under the weather while the bacteria is launching an all out attack on her child. The cause of those deaths regularly go undetected. This whole thing renders jokes about husbands being sent out on late night runs for pickles and ice cream soberingly unfunny.

From the legal perspective the creation of databases of the genetic fingerprints of pathogens will obviously increase the number of plaintiffs in the future as more silent outbreaks are discovered and previously unknown victims from the past are identified. It will also create some interesting legal issues. Take for instance Texas’ two year statute of limitations in Wrongful Death cases. There’s no discovery rule to toll the claim in large part because death is an easily appreciated clue that something has gone wrong and those who suffered the loss have two whole years to figure out the cause. Here though the ability to discover the cause didn’t exist in 2010. But of course if we start to draw the line somewhere else the debate over where is quickly overrun by the horrid thought of people digging up Granny who died of listeriosis back in 1988 to see if the genetic fingerprint of her killer matches one from a growing list of suspects. And let’s not forget about L. monocytogenes’ aiders and abettors, the other types of bacteria with whom it conspired to form the biofilm that protected L. monocytogenes from the disinfectants used to clean the food processing equipment. The promiscuous bugs likely acquired their special skill thanks to horizontal gene transfer not just among their own phyla but any passing bug with a helpful bit of code (like one that protects against the chemical agents, scrubbing and high pressure sprays used to disinfect food processing equipment) – and none of them were spontaneously generated at the ice cream factory. They all came from somewhere else.

Ultimately what makes claims arising out of the transmission of pathogens so different from other mass torts is that there is none of the usual causal uncertainty because, for example, the only cause of the 2010 patient’s listeriosis was Listeria monocytogenes that came from a particular flavor of ice cream that came from a particular plant. So what makes today’s news important is not that science can now answer “where did it come from and how many were infected?” but rather that science now asks in reply “how far back do you want to go?”