THE 1997 FLU OUTBREAK
The city of Hong Kong, China was a city of bird lovers. Many of the citizens were passionate birdwatchers; Kowloon's Yuen Po Street Bird Garden was a favorite of locals and tourists alike, and the poultry industry thrived. However, this all changed in 1997, when chickens began dying on farms in Hong Kong…
In March 1997, chickens were dying of a mysterious illness on three farms in the New Territories, Hong Kong. The mystery illness had wiped out more than 75 percent of the chickens on the three farms, or 6,500 chickens lost. "It's an ugly business. The virus spreads through the bloodstream to infect every tissue and organ; the brain, stomach, lungs, and eyes all leak blood in a body-wide hemorrhage until, from the tips of their combs to the claws on their feet, the birds literally melt," says Peter Davies, a witness to the 1997 H5N1 outbreaks.
Researchers in Hong Kong attributed the illness to the highly pathogenic avian influenza (HPAI) strain H5N1, which was first identified in 1959. Hong Kong authorities killed the remaining chickens on the three farms, and as a result, the virus seemingly disappeared.
Was it possible for humans to fall ill because of H5N1? Most thought it was not possible for H5N1 to make the species jump from bird to human. Hong Kong researchers had tried unsuccessfully to infect humans with various avian influenza subtypes. It was widely believed that avian influenza viruses could only infect birds and the occasional pig. They were wrong.
In May 1997, a three-year old boy was rushed to the Queen Elizabeth Hospital in Kowloon with a sore throat, fever, and abdomen pain. Doctors gave him various antibiotics, but all they could do was watch helplessly as the boy's condition steadily worsened. He died 6 days later, suffering from a number of symptoms, which included viral pneumonia, acute respiratory distress syndrome (ARDS), and kidney failure. Flu experts and doctors were surprised when samples from the boy's windpipe tested positive for H5N1. This particular strain was similar to the one that had killed the chickens in March, but a hemagglutinin mutation had allowed the virus to infect the boy. Scientists were shocked to discover that H5N1 had made the species jump, but they dismissed it as 'a fluke'. They seemed to be right, for no other cases were reported for several months.
Then, during November and December, H5N1 was back in the news when 17 people, between the ages of 1 and 60, fell ill. They had many of the same symptoms as the case in May: fever, sore throat and a cough. Severe pneumonia, gastronomical manifestations, elevated liver enzymes, and renal failure were some of the more serious symptoms. While most of the children under 13 fully recovered, most of the older patients were severely diseased. Out of the 17 new cases, 5 of them died. The sudden return of H5N1 in Hong Kong prompted virologists from around the world to investigate. It became clear that poultry and live-bird markets were the main sources: virologists isolated H5N1 samples from 20% of fecal samples from chickens and 2% from ducks and geese. Fearing a 1918-style pandemic, health experts pressured the government to kill all the birds in the city. Finally, on December 27, the government called for the destruction of every bird (1.5 million) in the city, as well as disinfection of the city's bird markets. In addition, live bird imports from neighboring province Guangdong were halted. These measures seemed to work, and everyone around the world sighed with relief as a pandemic was averted. However, this would not be the last the world would see of H5N1.