I'm new here, I think this is the right area for this but if its not, my apologies!

So heres the problem I need help solving:

There are 3 time periods, we'll call them 1, 2 and 3. In each time period there is a variable treatment the people are receiving, a, b, c or d. In time period 3 there is also a 5th treatment e. The number of people in each treatment group is also different.

It looks sort of like this:
Total number of people......Total Sick
Time period 1
Treatment A.......22,000.................545
Treatment B........9,000..................77
Treatment C........13,000................413
and so on for each time period...

My questions are 1) How do I find out whether there is a statistically significant difference between the different treatments (t-test maybe? what kind of t test?). And 2) How do I compare the different time periods to each other, i.e. how do I show if there is statistical significance between Time Period 1's different treatments and time period 2's different treatments?

Thanks in advance for you help!