Reported cases vastly underestimate mpox infections
Edwards R358
Abstract: Current CDC guidance stipulates that asymptomatic mpox infections are uncommon and play no role in transmission. However, transmission of mpox has continued since implementation of JYNNEOS vaccination in response to the 2022 mpox outbreak, marked by sporadic detection of clinical cases without known transmission links. To better understand this persistence, we undertook a prospective study testing for asymptomatic or paucisymptomatic mpox infection in 2,365 rectal swabs obtained from males through routine gonorrhea/chlamydia screening in Kaiser Permanente Southern California clinics in Los Angeles between May and October, 2024. Identifying roughly 0.7% infection prevalence over this period, we estimate that only one out of every 24.0 (95% CI: 15.0-39.2) mpox infections are ascertained through clinical testing of symptomatic persons. This reporting fraction varies according to characteristics expected to influence disease severity: one out of every 9.4 (5.0-18.2) unvaccinated infections and one out of every 34.6 (18.6-63.7) vaccinated infections is detected, while one out every 8.5 (3.8-20.3) infections among HIV-positive individuals and one out of every 28.9 (17.1-48.5) infections among HIV-negative individuals is detected. Phylogenetic analyses of mpox sequences from the Los Angeles area confirm this estimated reporting fraction, along with meta-analysis comparing data from passive case surveillance to studies employing symptom-agnostic molecular or serological testing during the 2022 outbreak. Our findings indicate most clade II mpox infections do not result in clinical detection even among persons connected to sexual health services, and suggest reported cases vastly underestimate true infections. This talk will address the statistical methods underlying our analysis framework, and attempt to unpack features of the study design and inference frameworks informing current public health guidance that downplays the significance of asymptomatic infections.
Reading list: do not take this as an endorsement of the papers, but rather as background coming into the talk.