Extreme heat may be crucial factor in human spread of bird flu The GuardianChicken culling, disposal raise concern as bird flu spreads ReutersFive people infected as bird flu appears to go from cows to chickens to humans Ars TechnicaBird Flu Infects 5 People in Colorado After Likely Cow-to-Poultry Spread ScienceAlertMore People Test Positive For Bird Flu In US The Weather Channel