Well, not exactly. Diseases always hit "Third World" countries the hardest; there's a lessened capacity (or will) to properly distribute any inoculation or cure. For two places with equal population, one that's First World (the UK, for example), one that's Third World (say, Ethiopia), you'll see a radically different impact of the disease.
Now, these are WAGs, but they're educated WAGs. Using the example of Great Britain and Ethiopia, a standard population of 58 million (which they shared in 1996), and the declared 25% global die-off from the two VITAS plagues being the average baseline, you lose a total, between the two countries, of 29 million lives. However, Great Britain would lose a third of that - call it 10 million, 17.24%, not quite one out of six people - while Ethiopia loses 19 million, 32.76%, or almost 1 out of 3 people. It may, in fact, be even worse than that; Great Britain might lose 10%, 5.8 million, while Ethiopia would lose 23.2 million, or forty percent of their population.
The US/Canada/UCAS? It's going to be the 10-15% benchmark. Parts of Sub-Saharan Africa? ... 50% might be generous.