Throat and nose membranes hurt by dry air allow cold viruses to enter more easily. It is important to carry out sensible counter plans against the cold with heaters and against the dryness with humidifiers.
In short, it is because the 'plan.doc' file I attached in the previous email was infected with a virus.
Something else to be borne in mind here is the rapidity with which the virus can reproduce.
Apparently my anti-virus software is not up to snuff.
That looks like the work of a virus.
Because of that virus, many elephants lost their lives.
Scientists are fighting to stem the spread of the AIDS virus.