A Decrease in Temperature and Humidity Precedes Human Rhinovirus Infections in a Cold Climate.
Both temperature and humidity may independently or jointly contribute to the risk of human rhinovirus (HRV) infections, either through altered survival and spread of viruses in the environment or due to changes in host susceptibility. This study examined the relationship between short-term variations in temperature and humidity and the risk of HRV infections in a subarctic climate. We conducted a case-crossover study among conscripts (n = 892) seeking medical attention due to respiratory symptoms during their military training and identified 147 HRV cases by real-time PCR. An average temperature, a decline in daily ambient temperature and absolute humidity (AH) during the three preceding days of the onset (hazard period) and two reference periods (a week prior and after the onset) were obtained. The average daily temperature preceding HRV infections was -9.9 ± 4.9 °C and the average AH was 2.2 ± 0.9 g/m³. An average (odds ratios (OR) 1.07 (95% confidence interval (CI) 1.00-1.15)) and maximal (OR 1.08 (1.01-1.17)) change in temperature increased the risk of HRV infections by 8% per 1 °C decrease. An average (OR 1.20 (CI 1.03-1.40)) and maximal decrease (OR 1.13 (CI 0.96-1.34)) in AH increased the risk of HRV infection by 13% and 20% per 0.5 g/m³ decrease. A higher average temperature during the three preceding days was positively associated with HRV infections (OR 1.07 (CI 1.00-1.15)). A decrease rather than low temperature and humidity per se during the preceding few days increases the risk of HRV infections in a cold climate. The information is applicable to populations residing in cold climates for appropriate personal protection and prevention of adverse health effects.
Center for Environmental and Respiratory Health Research, University of Oulu, P.O. Box 5000, FI-90014 Oulu, Finland. tiina.ikaheimo@oulu.fi.|Medical Research Center, University of Oulu and Oulu University Hospital, FI-90014 Oulu, Finland. tiina.ikaheimo@oulu.fi.
Tiina M
TM
Ikäheimo
Center for Environmental and Respiratory Health Research, University of Oulu, P.O. Box 5000, FI-90014 Oulu, Finland. kari.jaakkola@mil.fi.|Centre for Military Medicine, the Finnish Defence Forces, P.O. Box 5, FI-11311 Riihimäki, Finland. kari.jaakkola@mil.fi.
Kari
K
Jaakkola
Faculty of Medicine, University of Oulu, P.O. Box 5000, FI-90014 Oulu, Finland. jari.jokelainen@oulu.fi.|Unit of General Practice, Oulu University Hospital, FI-90220 Oulu, Finland. jari.jokelainen@oulu.fi.
Jari
J
Jokelainen
Impact Assessment Unit, Department of Health Protection, National Institute for Health and Welfare, P.O. Box 310, FI-90101 Oulu, Finland. annika.saukkoriipi@thl.fi.
Annika
A
Saukkoriipi
Viral Infections Unit, Department of Infectious Disease, National Institute for Health and Welfare, P.O. Box 30, FI-00271 Helsinki, Finland. merja.roivainen@outlook.com.
Merja
M
Roivainen
Department of Otorhinolaryngology Kainuu Central Hospital, Sotkamontie 13, FI-87140 Kajaani, Finland. raija.juvonen@kainuu.fi.
Raija
R
Juvonen
Medical Research Center, University of Oulu and Oulu University Hospital, FI-90014 Oulu, Finland. olli.vainio@oulu.fi.|Northern Finland Laboratory Centre (NordLab), FI-90220 Oulu, Finland. olli.vainio@oulu.fi.|Research Unit of Biomedicine, Department of Medical Microbiology and Immunology, P.O. Box 5000, FI-90014 Oulu, Finland. olli.vainio@oulu.fi.
Olli
O
Vainio
Center for Environmental and Respiratory Health Research, University of Oulu, P.O. Box 5000, FI-90014 Oulu, Finland. jouni.jaakkola@oulu.fi.|Medical Research Center, University of Oulu and Oulu University Hospital, FI-90014 Oulu, Finland. jouni.jaakkola@oulu.fi.
Jouni J K
JJ
Jaakkola
D003081:Cold Climate; D003080:Cold Temperature; D003139:Common Cold / Q000453:epidemiology*; D018592:Cross-Over Studies; D004781:Environmental Exposure; D006801:Humans; D006813:Humidity; D008297:Male; D008889:Military Personnel; D016133:Polymerase Chain Reaction; D012229:Rhinovirus / Q000302:isolation & purification*; D055815:Young Adult
absolute humidity; human rhinovirus; low temperature