"South China Sea" . "Populated coastal places in Hong Kong" . "Metropolitan areas of China" . "Special administrative regions of China" . "Populated places established in 1842" . "Influenza vaccines" . "Infraspecific virus taxa" . "Chinese-speaking countries and territories" . "Environmental social science" . "Influenza A virus subtype H1N1" . "English-speaking countries and territories" . "Port cities and towns in China" . "States and territories established in 1997" . "Pearl River Delta" . "2009 swine flu pandemic" . "Hong Kong" . "1842 establishments in Asia" . "Epidemiology" .