As early as April, states began noticing an unusual number of cases of salmonella food poisoning due to Salmonella enteritidis or SE. In recent years, SE has become the most common cause of salmonella infections in the U.S. It's predominantly found in eggs.
Aided by the CDC, health departments in 10 states identified 25 SE outbreaks among people who ate at the same restaurant or event where food was served. Fifteen of these restaurants served eggs traced to a single firm in Iowa, Wright County Egg.
However, on Aug. 20, a second Iowa firm -- Hillandale Farms of New Hampton -- issued a recall of eggs because of lab-confirmed illnesses associated with the eggs.
The FDA expects the recall to expand.
How many people are sick?
As of mid-July, the CDC had 2,000 confirmed reports of SE illness -- 1,300 more cases than usual for this time of year.
Most cases of salmonella do not get reported. The CDC usually calculates that for every reported case, 38 people are sickened. That would mean that the outbreak may already have sickened some 76,000 Americans. And the CDC expects to receive more reports before the outbreak is over.
The FDA says it's the biggest outbreak in recent history. But perspective is needed. The FDA calculates that there are 141,990 egg-related SE illnesses each year in the U.S.
The FDA calculates that about 91% of salmonella cases are mild -- that is, don't require a doctor visit and get better in one to three days. About 8% of cases are moderate, requiring a doctor visit and two to 12 days for recovery. And just over 1% of cases are severe, requiring hospitalization and 11 to 21 days for recovery. A small number of patients die.
Moreover, 3.7% of patients have lingering arthritis even after their other salmonella symptoms resolve. For 2.4% of patients, this arthritis lasts for a year or longer.
So far, all of the recalled eggs were packaged on Aug. 17 or earlier. This means that the "sell by" dates stamped on the egg cartons may not yet have expired. (The packing date is stamped on the egg carton using the "Julian date" or the numbered day of the year. Jan. 1 is Julian date 1; Aug. 17 is Julian date 229, as 2010 is not a leap year).