Is atheism a belief?

[Belacqua]

You see it's a simple observation.

The simple observation, if it's remembered and known as a data point, is knowledge or belief. 

I observe that there are many highly religious nations with horrible infant mortality rates.

To connect these two things -- to say that lots of religion is the cause of high infant mortality -- requires analysis and the application of some theory. So while simple observation may be enough to see A and B, determining the extent to which A is the cause of B is more than observation. 

For example, it may be that a low level of education is the cause of both high levels of religion and high infant mortality. So to blame religion based merely on the observation that those two things occur together may be too hasty.