Just weeks after Abbott Nutrition restarted production of baby formula at its plant in Sturgis, Michigan, the company announced Wednesday that massive flooding in the region has forced it to temporarily close the facility again.

"Severe thunderstorms and heavy rains came through southwestern Michigan on Monday evening, resulting in high winds, hail, power outages and flood damage throughout the area," Abbott said in a statement Wednesday.

The torrential downpour overwhelmed Sturgis' stormwater system and flooded numerous areas, including the plant. That forced Abbott to stop production of its EleCare specialty formula while it cleans and inspects the factory.

Abbott said the shutdown would "likely delay production and distribution of new product for a few weeks."

Abbott had only restarted the Sturgis plant on June 4, after it was closed for months following a voluntary recall of Similac and other brands produced there. The Food and Drug Administration had received complaints of potential bacterial exposure, though Abbott maintains there was no "conclusive evidence" linking products produced there to any illness or death.

The factory was a major supplier -- its closure fueled a nationwide shortage of infant formula that has left parents scrambling for months.

In Wednesday's release, Abbott said the facility would undergo "comprehensive testing" with an independent party to ensure it was safe to resume production.

Food and Drug Commissioner Robert Califf called the closure "an unfortunate setback," but said ramped-up production by Abbott and other manufacturers elsewhere, as well as increased imports, meant its impact would not be major.

Here's what you need to know about the infant formula shortage, including what caused it, why it's so serious, and how the re-closing of the Sturgis facility will impact it. 

Why do we have a baby formula shortage?

In September 2021, an infant in Minnesota given formula manufactured in Abbott's Sturgis factory was diagnosed with Cronobacter sakazakii, a potentially lethal bacteria.

Cronobacter is rare, but it can cause sepsis or meningitis and even lead to death in infants.

At least four more babies given formula from the Sturgis facility fell sick in the following months, three with Cronobacter sakazakii and one with Salmonella newport. Ultimately, two infants in Ohio died from Cronobacter infection. Another baby was hospitalized for three weeks before recovering.

As the infections were under investigation, the FDA received a report in October from an ex-employee alleging poor sanitation standards at the factory and the doctoring of records to hide inadequate quality checks.

After an FDA inspection of the facility in February, Abbott voluntarily recalled a number of batches of its Similac, Alimentum and EleCare infant formula brands. Abbott also ceased production at the factory.

Read more: How to Check if Your Baby Formula Has Been Recalled 

In a May 16 statement, Abbott said it conducts microbiological testing on products before distribution "and no Abbott formula distributed to consumers tested positive for Cronobacter sakazakii or Salmonella." It added that an investigation by the Centers for Disease Control and Prevention found no link between Abbott formulas and infant illnesses.

Still, Abbott is the largest of only a handful of baby formula manufacturers in the US and accounts for more than 40% of the market. Thus the recall and plant closure cratered supply. 

The crisis has also fueled formula hoarding, which has made the deficit worse, along with reports of price gouging. Some stores, including CVS and Walgreens, have limited customers to three formula purchases per visit. 

When will the shortage end?

Abbot restarted production of its EleCare and other specialty formulas on June 4 and, at the time, said it expected them to be available around June 20. Formulas for infants with special conditions that make them unable to consume traditional formula were being prioritized at the factory.

"We're also working hard to fulfill the steps necessary to restart production of Similac and other formulas and will do so as soon as we can," the company said in a June 4 release. "We will ramp production as quickly as we can while meeting all requirements."

But, on June 15, Abbott said a temporary closure due to flood damage meant production and distribution at the Sturgis plant would be delayed "for a few weeks." 

Califf, the FDA commissioner, said in a tweet Wednesday night that his agency was aware of the situation but added that "the all-of-government work to increase supply means we'll have more than enough product to meet current demand."

"Abbott has been exceeding the monthly quantity of formula that it produced in 2021 – all while the Sturgis facility is out of production," Califf said. "Other producers also continue to make formula at higher-than-average rates, and we continue to exercise flexibility to import additional formula."

The first batches of Nestlé formula arrived from Switzerland on May 23, bringing nearly 1.5 million 8-ounce bottles of Alfamino Infant, Alfamino Junior and Gerber Good Start Extensive HA, all of which are hypoallergenic varieties for children with cow's milk protein allergy.

The result is that, even before the Sturgis plant reopens, the total amount of formula available "exceeds the demand for formula prior to the recall," according to Califf. 

At a congressional hearing on May 25, after plans to increase production and imports were announced, Califf told lawmakers that store shelves wouldn't be fully restocked until at least July.

Why is the formula shortage such a big deal?

Less than half of newborns in the US are breastfed exclusively in the first three months of life, according to the CDC, and one in five are given formula in the first few days. And by six months, 75% of babies receive some formula, according to the CDC.

Some mothers or babies have difficulty breastfeeding, and infants may be given formula to encourage weight gain. Changing formulas suddenly can cause digestive issues, and babies with allergies or certain medical conditions require specific formulas.

"If your baby is allergic to standard formulas and you need a broken-down formula, then it's critical that you stick to that same type of formula," Steven Abelowitz, medical director of Coastal Kids Pediatrics in Orange County, California, told CNET previously.

The shortage isn't impacting all Americans equally, either. 

"The families who have fewer resources, have fewer options, who aren't able to pay premium prices are going to be more at risk," Ann Kellams, board president of the Academy of Breastfeeding Medicine, told Vox.

The Special Supplemental Nutrition Program for Women, Infants, and Children, a federal program commonly known as WIC, provides food assistance to low-income families. Individual states dictate which brand of formula is covered by WIC, and Abbott Nutrition's Similac formula, the leading brand in the US, is one of the major suppliers to the WIC program.

That means parents of the estimated 1.7 million infants in the WIC program have had fewer options. 

Read more: What to Do if You're Running Low on Formula

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.