1.   But they are certainly around, spreading flu and doing other jobs of which we are unaware.

2.   As yet, there are no answers on how the flu is spread.

3.   They concluded that vaccinating schoolchildren, the group that spreads flu the most, helps protect senior citizens.

4.   Cages used to transport birds in markets could play a major role in spreading avian flu if they are not cleaned and disinfected properly, the report said.