The study by Lowen et al. investigates the impact of relative humidity (RH) and temperature on the transmission of influenza virus between guinea pigs. Using a controlled environment, they found that both low RH (20%–35%) and cold temperatures (5 °C) favored the spread of the virus. At 20 °C, transmission was most efficient at low RH, while at 50% RH, only one out of four naive guinea pigs became infected. At 80% RH, transmission was blocked. At 5 °C, transmission was more frequent than at 20 °C, with peak viral shedding extending by about 2 days. The study also found that cold temperatures did not impair the innate immune response, suggesting that the increased transmission at 5 °C is due to other factors. The findings provide experimental evidence for the role of weather conditions in the dynamics of influenza, particularly in explaining the seasonal spread of the virus.The study by Lowen et al. investigates the impact of relative humidity (RH) and temperature on the transmission of influenza virus between guinea pigs. Using a controlled environment, they found that both low RH (20%–35%) and cold temperatures (5 °C) favored the spread of the virus. At 20 °C, transmission was most efficient at low RH, while at 50% RH, only one out of four naive guinea pigs became infected. At 80% RH, transmission was blocked. At 5 °C, transmission was more frequent than at 20 °C, with peak viral shedding extending by about 2 days. The study also found that cold temperatures did not impair the innate immune response, suggesting that the increased transmission at 5 °C is due to other factors. The findings provide experimental evidence for the role of weather conditions in the dynamics of influenza, particularly in explaining the seasonal spread of the virus.