Key points
Epidemiologic and traceback data show that fresh, slivered onions served at McDonald’s were the likely source of this outbreak. Affected onions served at McDonald's locations were recalled and are past shelf life.
When people got sick
This chart shows when the 104 people in this E. coli outbreak got sick.
Recent illnesses may not yet be reported as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak. The true number of sick people in this outbreak is also likely much higher than the number reported. This is because many people recover without medical care and are not tested for E. coli.