Low Risk of Clade 1 Mpox Spread During Air Travel Revealed

Contact tracing efforts following mpox clade I infections on commercial flights have found no evidence of secondary transmission, indicating a low risk of spread during air travel, according to a recent report from the Centers for Disease Control and Prevention (CDC).

The CDC’s Notes from the Field report, published in the Morbidity and Mortality Weekly Report (MMWR), details contact tracing conducted among 60 aircraft contacts of three individuals with laboratory-confirmed clade I monkeypox virus (MPXV) who traveled on five commercial flights between November 2024 and January 2025. Despite close proximity during flights, no secondary cases were identified among those monitored.

This finding aligns with prior observations regarding clade II MPXV, where transmission risk during commercial air travel has likewise been shown to be low. However, researchers noted that while data suggest clade I MPXV might be more transmissible than clade II in certain settings, the available evidence does not support increased transmission via air travel.

The CDC discontinued routine aircraft contact investigations for all MPXV clades and subclades in 2025, citing the consistently low yield of secondary cases identified through such efforts. The agency emphasized that monkeypox is primarily transmitted through close, sustained physical contact, not casual proximity such as that encountered during flights.

Clade I MPXV, which includes subtypes like clade 1b, has been associated with more severe disease compared to clade II and has historically been linked to travel in or from regions in Africa where zoonotic spillover occurs. Recent clade I cases in the United States, including the first identified in Novel York City in March 2026, have involved individuals with recent international travel histories.

While household and community transmission remain concerns—particularly in settings with crowded living conditions or limited healthcare access—the data continue to indicate that the risk of contracting mpox through air travel is minimal for both clade I and clade II strains.

Public health officials maintain that vaccination, awareness of symptoms, and isolation of infected individuals remain key strategies in preventing broader spread, especially as global travel resumes and surveillance systems monitor for emerging cases.