Actually, it’s dry air (too hot or too cold) that creates a room for viruses to enter your body ( check this](http://search.netscape.com/ns/boomframe.jsp?query=winter+viruses+heating&page=1&offset=1&result_url=redir%3Fsrc%3Dwebsearch%26amp%3BrequestId%3D751962ad7a148e31%26amp%3BclickedItemRank%3D6%26amp%3BuserQuery%3Dwinter%2Bviruses%2Bheating%26amp%3BclickedItemURN%3Dhttp%253A%252F%252Fwww.idph.state.il.us%252Fpublic%252Fhb%252Fhbwinter.htm%26amp%3BinvocationType%3D-%26amp%3BfromPage%3DNSCPResults&remove_url=http%3A%2F%2Fwww.idph.state.il.us%2Fpublic%2Fhb%2Fhbwinter.htm) and this](WebMD - Better information. Better health.) ). Also heat from heating systems especially those run by gas can produce air pollution(dust??) and you know that air pollution is one of the main causes of bronchitis (
read this](WebMD - Better information. Better health.) ). Most people don’t get out much during winter season so they don’t get enough fresh air so IMO, it’s good to leave a window open(okay, how abt a half window?) to let the fresh air in. Sahi hai na Daacter saab? 
Take care of yourself bro. 