At the center of the current baby formula shortage is the contamination of baby formula linked to Cronobacter sakazakii. Illnesses from this bacteria are rare, but can lead to deaths, especially in infants.
The Centers for Disease Control and Prevention receives reports of two to four infections in infants per year. This is likely underreported.
Cronobacter thrives in dry environments. It can live in dry foods, such as baby formula, powdered milk, herbal teas, and starches. Most states are not required to report cases, so doctors are not required to report cases of Cronobacter to health departments.
This bacteria lives naturally in the environment. Food can become contaminated with Cronobacter in several ways, such as during manufacturing, from contaminated raw materials, or contamination from the home environment. So simply laying the measuring scoop on a contaminated countertop, using contaminated water, or a contaminated bottle can lead to problems.
Source: Cronobacter and Powdered Infant Formula Investigation—CDC