The above map from The Economist is a useful guide to understanding the sheer size of China's population. We should always think about this in assessing the threat of a disease like H7N9. For any given individual, the odds of contracting H7N9 are truly minuscule.
Let's look at the four provinces with the most cases. Zhejiang's population is about 54.7 million (equivalent to Myanmar). The province has so far recorded 83 cases, which means that one in 659,000 residents has contracted the disease. Shanghai has 23.7 million people, (equivalent to Cameroon) and 40 cases, or one per 592,000 residents.
Jiangsu's 78.6 million are equivalent to Iran, and its 31 cases mean those patients have contracted H7N9 against odds of 2.5 million to one. And Guangdong, with 105.9 million, is equivalent to the Philippines. Each of its 26 cases is one in 4 million.
So why are China and the rest of us paying so much attention to this almost non-existent disease when, since January 1, over 60,000 worldwide have died of malaria? And 103,587 have died of HIV/AIDS? And 468,382 children under 5 have died (most from diarrhea)? And 800,000 have died of various communicable diseases?
Perhaps we've tuned out on those death tolls, made them background noise, out of sheer self-preservation. Click through that malaria link to Worldometers and you can watch the numbers growing before your eyes. (Click on "this year" and see how many have died so far today.)
We pay attention to the novel infections, I suspect, precisely because they're novel. We've already factored in (that is, learned to ignore) the routine diseases. But H5N1, H7N9, and H10N8 are new, mysterious, and therefore potentially as bad as malaria or diarrhea. So we jump every time another unlucky chicken vendor falls ill on the far side of the world.
We also remember when H1N1 came out of nowhere four years ago and spread around the world as fast as jetliners could carry it. If it had developed a case fatality rate like that of H5N1, we'd still be speaking of it in hushed tones, instead of shrugging it off as WHO losing its bureaucratic cool. But we sense just such a fatal pandemic in every new flu strain.
So we study each strain like military intelligence officers, as if its genome carried an enemy's plans for invasion and conquest. In the process, we learn more about the influenzas in general, so what H5N1 or H7N9 reveals could be used in a counterattack against other strains.
The same could be true of MERS, if we could ever figure out how the hell people catch it except from other people. (Just to be on the safe side, I have totally abstained from kissing camels and bats.)
So the attention we pay to these fringe viruses is certainly worth the effort. I just wish it were politically possible to attack the routine diseases as well—and do it so successfully that governments have to start worrying about jobs for all those toddlers who will now grow up into healthy young adults instead of dying before age 5.