In the wake of the hepatitis A outbreak that has killed three people and sickened over 500 in the Pennsylvania area in recent weeks, it is important to remember how useful it is to be able to track cases of disease and identify their sources. For a reminder of how not to track disease (that is, in an anecdotal and highly subjective fashion that may confuse coincidence with causality), see ACSH's booklet on Cancer Clusters.
For an example of an effort to collect data on reports of foodborne illnesses or to report an illness if something you've eaten has made you sick check out the site described in the press release below. There is always some risk that lay readers will use the site to "find" patterns of foodborne illness that don't really exist as the site itself discusses at some length here: http://www.rusick2.msu.edu/phantom.asp but some effort is made to minimize site users' trawling of data and to impress upon them the difference between mere apparent clusters of disease and confirmed outbreaks. The site has already been helpful in identifying real outbreaks and particularly given new concern about tracking possible biological terror attacks may be a model of interactive tracking for the future. Or as the makers of the site put it:
There is a website available to help identify clusters of individuals who became ill after eating the same contaminated food item...the RUsick2 Forum is at www.RUsick2.msu.edu or www.foodsafe.msu.edu and was developed by food safety experts at the National Food Safety & Toxicology Center at MSU. If you or someone you know suddenly develops unexplained vomiting and/or diarrhea, visit the RUsick2 Forum to see if other sick people reported eating the same food that you ate. The website has been around for nearly one year and has received nearly 1300 reports from all over the United States. It has assisted in identifying foodborne illness outbreaks in the Greater Lansing[, Michigan] area, where it began.