Investigation and Results

A confirmed case was defined as illness in a resident of San Diego County who had 1) clinically compatible signs or symptoms of botulism during September 2017–May 2018; 2) laboratory detection of botulinum neurotoxin (BoNT) in serum; 3) a history of injection drug use during the 2 weeks before illness onset; and 4) no suspected exposure to a contaminated food. A probable case was defined similarly, but without laboratory confirmation. All wound botulism patients reported to COSD were asked by investigators about potential exposures using a standardized questionnaire. Self-reported history of injection drug use was recorded for each patient, with drug use corroborated by toxicology results when possible. Serum collected from each patient was tested for BoNT by mouse bioassay at the California Department of Public Health’s Microbial Diseases Laboratory; serum specimens with indeterminate results were tested by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry at CDC. Direct hospital charges for the outbreak-associated patients were estimated based on hospital charges for wound botulism cases reported to COSD during 2005–2016 from the California Office of Statewide Health Planning and Development database.*

Among nine total cases, eight patients were men; median age was 40 years (range = 25–67 years). Symptom onset dates ranged from September 26, 2017, (epidemiologic week 39) to April 12, 2018 (epidemiologic week 15) (Figure). The most frequently reported symptoms were muscle weakness, difficulty swallowing, and blurred vision (Table 1). Abscesses were observed for five patients. Symptoms of wound botulism were initially attributed to drug intoxication for four patients. One patient was admitted for 7 days before receiving BAT and died 9 days later at a long-term care facility. One patient had received the opioid overdose reversal medication naloxone without improvement in symptoms, and one patient had received 2 doses of naloxone upon admission after at least one previous emergency department visit associated with wound botulism. A fourth patient, who was evaluated for symptoms of wound botulism and a history of close contact with a person known to have wound botulism, was discharged from the hospital before later being readmitted. All nine patients required admission to the intensive care unit; six required endotracheal intubation and mechanical ventilation, one of whom died. Median duration of hospitalization was 15 days (range = 9–67 days) until discharge to long-term care facilities (eight, including the patient who died) or departure against medical advice (one). All patients reported history of injecting heroin; seven reported using black tar heroin, six injected heroin by skin popping, and one patient did not report injection method. Toxicology tests performed for six patients were all positive for opioids. Two patients reported close contact with each other that included sharing drugs and needles.

In coordination with COSD, the California Department of Public Health authorized BAT, which was released for nine patients by CDC quarantine stations in Los Angeles (eight) and San Francisco (one). Median interval from symptom onset to BAT administration was 6.5 days (range = 2.7–10.5 days) (Table 2). Pre-BAT serum specimens from nine patients were collected for testing; BoNT type A was confirmed for six patients by mouse bioassay and two patients by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. BoNT was not detected for one patient; however, that serum sample was frozen and hemolyzed and therefore not in optimal condition for confirmatory testing.

During the 2017–2018 outbreak, all nine patients were enrolled in public health care programs, including Medi-Cal† (seven), Medicare (one), and the Veterans Health Administration (one). The total direct hospital costs for this outbreak was estimated at $2.3 million, for 203 total in-patient days charged at the historical median daily rate of $11,506 per day, based on data available for nine patients hospitalized with wound botulism in San Diego County during 2005–2016 (COSD, unpublished data; 2018).