Tracking the Next Killer Flu

Thai farmer Noi Tritanasombat waits for a health worker to test his ducks for the H5N1 virus. Such measures have checked the spread of bird flu in Thailand, but outbreaks elsewhere in Asia pose a continuing threat. The virus could evolve into a form that passes easily from person to person—and could spread around the world by jet.


Written by Tim Appenzeller

Republished from the pages of National Geographic magazine

Little Ngoan was buried behind her parents' hut three weeks ago. Her grave, a bulky concrete tomb like others dotting the Vietnamese countryside, rests on high ground between a fishpond and yellow-green rice fields. At one end her family laid out her cherished possessions: a doll's chair, a collection of shells, plastic sandals. They painted her tomb powder blue.

While Ngoan's parents are off helping with the rice harvest, other relatives share their memories. "She was so small, just ten years old," says her grandmother, sitting on a hammock. "She was very gentle and a good student. If you look at her older sister"—the 17-year-old hangs back shyly—"you can imagine what she was like." Ngoan's grandfather, silent with grief, lights a stick of incense at her grave.

The loss of a beloved child has hit this family hard. But ordinarily, the wider world would pay little attention to a child's death from infectious disease in this remote corner of Vietnam's Mekong Delta. Old scourges like dengue fever and typhoid still take a toll here, and HIV/AIDS is on the rise.

Yet Ngoan's death and more than 50 others in Southeast Asia over the past two years have raised alarms worldwide. Affected countries are struggling to take action; other nations are sending aid and advisers while stockpiling drugs and developing vaccines at home. And scientists have stepped up their research into the fateful traffic of disease between animals and people.

Why? Because Ngoan died of the flu.

To most of us, flu is a nuisance disease, an annual hassle endured along with taxes and dentists. Some people think a flu shot isn't worth the bother. But flu is easy to underestimate. The virus spreads so easily via tiny droplets that 30 million to 60 million Americans catch it each year. Some 36,000 die, mostly the elderly. It mutates so fast that no one ever becomes fully immune, and a new vaccine has to be made each year.

That's ordinary flu. But the disease that is taking lives in Southeast Asia is no ordinary flu. Its primary victims have been chickens, more than a hundred million of them, killed either by the virus or in often futile control efforts. It's not unusual for chickens to get flu; in fact, avian-flu viruses far outnumber human ones. But Robert Webster of St. Jude Children's Research Hospital in Memphis has studied flu viruses for 40 years and has never seen the likes of the one that killed Ngoan.

"This virus right from scratch is probably the worst influenza virus, in terms of being highly pathogenic, that I've ever seen or worked with," Webster says. Not only is it frighteningly lethal to chickens, which can die within hours of exposure, swollen and hemorrhaging, but it kills mammals from lab mice to tigers with similar efficiency. Here and there people have come down with it too, catching it from infected poultry like the chickens that died on Ngoan's farm a few days before she fell ill. Half the known cases have died.

In those deaths many public health experts hear the distant rumblings of a catastrophe. So far this virus—classified as H5N1 for two proteins that stud its surface like spikes on a mace—isn't good at passing from birds to people, let alone from one person to the next. "It can make that first step across, but then it doesn't spread easily from human to human," says Webster. "Thank God. Or else we'd be in big trouble."

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Great Wall History

The history of the Great Wall is said to start from the Spring and Autumn Periods when seven powerful states appeared at the same time. In order to defend themselves, they all built walls and stationed troops on the borders. At that time, the total length of the wall had already reached 3,107 miles, belonging to different states.

In 221 BC, the Emperor Qin absorbed the other six states and set up the first unified kingdom in Chinese history. In order to strengthen his newly born authority and defend the Huns in the north, he ordered connecting the walls once built by the other states as well as adding some sections of his own. Thus was formed the long Qin's Great Wall which started from the east of today's Liaoning Province and ended at Lintao, Gansu Province.

In the Western Han Dynasty, the Huns became more powerful. The Han court started to build more walls on a larger scale in order to consolidate the frontier. In the west, the wall along the Hexi corridor, Yumenguan Pass, and Yangguan Pass was built. In the north, Yanmenguan Pass and Niangziguan Pass in Shanxi were set up. Many more sections of the wall extended to Yinshan Mountain and half of the ancient Silk Road was along the Han's wall.

The Northern Wei, Northern Qi and Northern Zhou Dynasties all built their own sections but on a smaller scale than the walls in the Han Dynasty. The powerful Tang Dynasty saw peace between the northern tribes and central China most of the time, so few Great Wall sections were built in this period.

The Ming Dynasty is the peak of wall building in Chinese history. The Ming suffered a lot by disturbances from minority tribes such as the Dadan, Tufan and Nuzhen. The Ming court from its first emperor to the last ceaselessly built walls in the north. The main line started from Jiuliancheng near the Yalu River in the east to the Jiayuguan Pass in the west and measured over 4,600 miles. Besides adding many more miles of its own, the Ming emperors ordered enlargement of the walls of previous dynasties into double-line or multi-line walls. For example, out of Yanmenguan Pass were added three big stone walls and 23 small stone walls. Eleven Garrisons were distributed along the main line of the wall. The countless walls, fortresses, and watch towers made the country strongly fortified. In the early Qing Dynasty, some sections of the walls were repaired and several sections were extended. This great engineering work stopped in the middle of the Qing Dynasty.

Owing to its long history, natural disasters and human activities, many sections of the Great Wall are severely damaged and disappearing. Being a world-famous engineering project and witness to the rise and fall of Chinese history, the Great Wall, needs us to take immediate action to protect it!