California health officials say they have identified cases of infant botulism with exposure to powdered infant formula that occurred prior to the current multistate outbreak.

In a statement, a spokesperson for the California Department of Public Health (CDPH) said the state has identified at least six cases of infant botulism with exposure to ByHeart powdered infant formula that occurred from November 2024 to June 2025. The 15-state outbreak currently being investigated by the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA), which includes four sickened infants in California and 31 nationwide, began on August 1, 2015.

"CDPH is continuing investigate, but at this time we cannot connect any pre-August 1 cases to the current outbreak," the CDPH spokesperson said.

The statement explained that in early 2025 there was not enough evidence to immediately suspect a common source among the six suspected cases, and that the number of cases were within expected case numbers based on previous years' trends.

CPDH has played a critical role in investigation

Infant botulism occurs when a baby swallows Clostridium botulinum spores, which can grow in the intestine and produce toxins that cause constipation, poor feeding, loss of head control, and difficulty swallowing. 

CDPH's detection of C botulinum in an opened can of ByHeart Whole Nutrition Infant Formula on November 8 led the FDA to recommend a recall of the product. Prior to the outbreak investigation, no powdered infant formula had tested positive for C botulinim in the United States.

CDPH said that, from August 1 through November 19, 107 infants nationwide have received treatment with BabyBIG, a human plasma-derived treatment for infants with botulism. That includes confirmed cases and infants who were being treated while awaiting test results. 

CPDH developed and is the only source of BabyBIG. The CDC and FDA began their investigation into the outbreak after officials with CPDH's Infant Botulism Treatment and Prevention Program alerted them to an increase in requests for the treatment.

US COVID, seasonal influenza, and respiratory syncytial virus (RSV) activity remains low but is growing in some parts of the country, according to the most recent respiratory illness update from the Centers for Disease Control and Prevention (CDC). 

The CDC monitors respiratory illness activity by looking at a range of diagnoses from emergency department (ED) visits, including the common cold, flu, RSV, and COVID. Nationally, levels of acute respiratory illnesses are low or very low, with only three states—Alabama, Arkansas, and New Hampshire—reporting moderate levels. 

Indiana and Arkansas report moderate levels of COVID, while rates remain low or very throughout the rest of the country. (Data from Arkansas are limited and may not represent levels across the whole state.)

Flu cases are rising in all but 10 states, and COVID-19 rates are rising in nine.

RSV increasing in preschoolers

RSV activity is on the rise in all but 15 states, with increasing ED visits among children aged 0 to 4 years in the South. 

The update also highlights elevated levels of Mycoplasma pneumoniae in some parts of the country, based on ED visits and positive tests. M pneumoniae can cause “walking pneumonia.” 

Pertussis, or whooping cough, cases remain higher in 2025 than they were immediately before the COVID-19 pandemic, even though they've declined since their peak in late 2024. Pertussis doesn’t follow a clear seasonal pattern, but cases often rise in summer and fall, and the disease is highly contagious. It poses the greatest risk to infants, and vaccination remains the best protection against severe outcomes.

Despite the global expansion of antibiotic awareness campaigns over the past decade, the public's understanding of antibiotics remains insufficient, researchers reported last week in Clinical Microbiology and Infection.

In a systematic review and meta-analysis, researchers from Australia, Nigeria, and the United Kingdom identified 227 studies from 98 countries that reported the knowledge of antibiotic use and resistance among the public. They found that 73.2% of the 322,492 participants correctly recognized that antibiotics are effective in treating bacterial infections and 72.5% knew that excessive antibiotic use reduces the effectiveness of antibiotics.

But only 42.1% knew that antibiotics were not effective against viruses, and that number was significantly lower in countries such as Laos (7.2%), Myanmar (11.7%), and Bangladesh (12.5%). Similarly, only 35.1% of respondents knew that antibiotics don't speed up recovery from cold and flu. 

The study authors note that a systematic review conducted in 2015—the year the World Health Organization declared antimicrobial resistance (AMR) a top 10 global health threat—reported that 46.1% of the public was aware that antibiotics are ineffective against viruses, which suggests a decade of public awareness campaigns has had little impact.

"This persistent misconception will continue to drive the misuse of antibiotics for viral infections, a widespread issue in many regions globally, thereby contributing to the broader challenge of AMR," they wrote. "The low levels of public knowledge regarding the ineffectiveness of antibiotics against viral infections suggest that current efforts and campaigns aimed at addressing antibiotic resistance remain insufficient."

Multifaceted strategies are needed

In addition, while 58.4% of respondents acknowledged antibiotic resistance as a global health threat, only 39.1% understood that antibiotic-resistant bacteria can be transmitted between individuals.

"Understanding that resistant bacteria can be transmitted from person to person is crucial, as interpersonal spread represents a key mechanism by which antimicrobial resistance propagates within communities," the authors wrote.

The authors conclude that multifaceted strategies are needed to enhance public knowledge of antibiotics.

"These strategies should include patient education by healthcare professionals, targeted outreach, mass media and digital campaigns, formal education, community-based interventions, robust policy and regulatory measures, and international collaboration," they wrote.