The influence of meteorology on the spread of influenza: survival analysis of an equine influenza (A/H3N8) outbreak.
Authors: Firestone Simon M, Cogger Naomi, Ward Michael P, Toribio Jenny-Ann L M L, Moloney Barbara J, Dhand Navneet K
Journal: PloS one
Summary
# Editorial Summary: Meteorological Influences on Equine Influenza Transmission Environmental conditions play a measurable role in how equine influenza spreads across premises, with relative humidity, temperature, wind speed and direction all significantly influencing infection risk during an outbreak. Researchers analysed data from a substantial A/H3N8 outbreak using geostatistical mapping and Cox regression modelling, matching meteorological conditions to each premises' location and timing of disease occurrence, with particular attention to how conditions three days prior predicted infection hazard—a lag that aligns with the virus's known incubation period. The analysis revealed that infection risk increased substantially when relative humidity dropped below 60%, peaked at temperatures outside the 20–25°C range, and notably intensified when wind speeds exceeded 30 km/hour blew from infected premises towards susceptible locations. These field-derived findings confirm laboratory observations about airborne virus stability in different humidity and temperature conditions, whilst introducing wind velocity as a previously under-researched factor in outbreak dynamics. For practitioners managing influenza risk, these associations suggest that meteorological forecasting could inform quarantine protocols and movement restrictions during outbreaks—tightening biosecurity measures particularly during dry, cool conditions or when winds favour aerosol transport from affected yards towards neighbouring facilities.
Read the full abstract on PubMed
Practical Takeaways
- •During influenza outbreaks, heighten biosecurity measures when conditions favour transmission: low humidity (<60%), moderate temperatures (20-25°C), and windy conditions — particularly from direction of known infected premises
- •Plan enhanced quarantine and monitoring protocols 3 days ahead of adverse weather conditions, as this lag time matches the virus incubation period
- •Use wind direction and speed forecasts as part of outbreak risk assessment to identify which premises are at greatest aerosol transmission risk from nearby infected horses
Key Findings
- •Relative humidity <60% and daily maximum air temperature of 20-25°C were significantly associated with hazard of equine influenza infection
- •Wind speeds >30 km/hour from direction of nearby infected premises increased hazard of infection
- •Meteorological effects on infection hazard were strongest when time-lagged by three days, corresponding to equine influenza incubation period
- •Geostatistical analysis of outbreak data provided field evidence confirming laboratory findings on environmental transmission mechanisms of influenza A