By Ethan Covey
An outbreak of nontypeable Haemophilus influenzae disease among children at an elementary school in Detroit resulted in three hospitalizations and one death in 2023 (MMWR Morb Mortal Wkly Rep 2024;73[32]:691-695).
In the United States, most cases of invasive H. influenzae disease are caused by nontypeable strains because there is no vaccine against them. Before the introduction of a Hib (H. influenzae type b) vaccine in the 1980s, Hib was the leading cause of bacterial meningitis among young U.S. children. An estimated 20,000 children younger than 5 years of age came down with severe Hib, and about 1,000 died. Most were younger than 12 months of age. By 2020, only about 15 children had Hib—a decline of more than 99%, according to immunize.org.
The Michigan outbreak occurred in May 2023, when the city health department was notified of four cases of invasive nontypeable H. influenzae among non-Hispanic Black elementary students who were part of the same grade. All four cases were 5 to 6 years old. Each of the children had disease onset within seven days of one another. Three of the children were hospitalized, and one died.
“This report documents that nontypeable H. influenzae can cause outbreaks, which is otherwise rarely documented in literature,” Denise Fair Razo, MPH, MBA, the chief public health officer of the Detroit Health Department, told Infectious Disease Special Edition.
Although chemoprophylaxis is not recommended typically for nontypeable cases, the report said rifampin was recommended “because of the high attack rate (four cases among 46 students; 8.7%).”
While rifampin was recommended for household contacts of the patients, as well as other students and school staff members, only 11% of students received the therapy. The health department said misinformation among caregivers and healthcare providers and difficulty obtaining chemoprophylaxis likely contributed to low coverage.
Despite the outbreak, Ms. Fair Razo said the investigation has not provided any indication that the incidence of nontypable H. influenzae is increasing in the United States.
“Secondary transmission is uncommon, and outbreaks are rare, although this report H. influenzae highlights the usefulness of updated chemoprophylaxis guidance in the event of another outbreak,” she said.
She hopes that future research will address lingering questions regarding H. influenzae and other infectious disease outbreaks.
“We’d be interested in understanding how interactions between health providers, administrators and the public influence participation in outbreak interventions, especially in the wake of the COVID-19 pandemic,” she said.
“Our team hypothesized pandemic fatigue played a role in the low uptake of chemoprophylaxis, despite it being widely available. This itself has wider implications in all kinds of infectious outbreaks, not just nontypeable H. influenzae.”
Ms. Fair Razo reported no relevant financial disclosures.
