Extensively drug-resistant TB is a new world-wide threat to human health. It can be carried by asymptomatic hosts who are still infectious, and communicate the disease. The Al-J channel had a story on this today, but I found a BBC link (there's an icon on my browser) from their correspondent in Geneva: http://news.bbc.co.uk/2/hi/health/7265464.stm Apparently this has caught the WHO by surprise; it's a result of poorly administered antibiotics and disease treatment, surprise surprise. Coming to your place anytime soon.