John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
Researchers say lethal strains of influenza are most likely to arise next in coastal China, the Nile Delta and elsewhere.
In 1968, an especially virulent flu popped up in Hong Kong and quickly spread around the world; by the time it had run its course, more than 1 million people had died. Such great pandemics are bound to be repeated through history. The question is, where will the next one hit, and can we do anything to minimize the damage?
It's "yes" to the latter question and "potentially a whole load of cities" to the first, according to a new study by an international team of researchers. The scientists from UCLA, the United Nations, Egypt's "National Laboratory for Quality Control on Poultry Production" and elsewhere have made their top picks for where the next deadly influenza epidemic could strike: China's coastal regions, the Nile Delta and eastern Asia head the list. They're urging governments in these places to keep a close bead on signs of a spreading flu, so they can throw a cap on it before it becomes a worldwide plague.
These researchers are interested in kinds of flu similar to the 1968 strain, hardhitting illnesses forged through the process of "reassortment" – two types of virus meeting inside a host to spawn an even more virulent entity. So they started looking for geographic areas with an overlap among human flu (H3N2) outbreaks, bird flu outbreaks (H5N1) and swine populations. The pigs were a necessary part of the puzzle because, the scientists note, they can act like a "mixing vessel for reassortment of subtypes H5N1 and H3N2."
Rooting out these possible hot zones was more difficult than it may sound. Some countries have flu-reporting systems that are shaky at best (looking at you, Indonesia), and in Egypt and China business-conscious farmers sometimes don't report sickness among their herds. So the scientists took multiple approaches: In Egypt, for example, they focused on districts that had more water, because people often raise chickens near irrigated fields and canals. They took urban density into account in places like China, as thickly populated cities are more conducive to the spread of disease. Other things they examined included regional temperatures, rainfall, amount of cropland and, when available, "chicken and duck density."
You can see their various approaches at work in this map of China's potential "influenza reassortment areas":
So where might the next superflu sprout forth? Here's their list of cities with the greatest chances of being exposed:
In Egypt: Cairo, Benha, Dumyat, El Faiyum and Shibin el Kom;
In China: Shanghai, Chengdu, Sichuan and Hangzhou (in general, the coastal provinces of Guangdong, Jiangsu, Shanghai, and Zhejiang, as well as the central provinces of Hunan and Sichuan);
Elsewhere in Asia: Seoul, South Korea; Delhi and Kanpur, India; Dhaka, Bangladesh; and southwestern Japan.
Just something to fret about during your next international trip. For more info, take a look at the full study in the journal Emerging Infectious Diseases, called "Predicting Hotspots for Influenza Virus Reassortment."
Top image depicts the risk of bird flu outbreaks in China. More complete version here.