Purdue News Service

No one has ever recorded a epizootic (an epidemic in an animal species) with this high mortality in such a large geographic area, says Dr. James Campbell, lead investigator of avian flu vaccine clinical trials at the University of Maryland School of Medicine. He calls this "unprecedented."

According to WHO, the most significant risk avian flu poses to humans isn't direct transmission from infected birds. The greater danger is that the human flu virus could meet and mingle with the avian flu virus. That could happen if a human, a bird, or even a pig, is infected with both at the same time.

The World Health Organization says the world is now closer to another influenza pandemic than at any time since 1968, when the last of the previous century's three pandemics occurred.

It reports that even a mild pandemic could kill 2 million to 7.4 million people and cost $330 billion.

The Spanish flu pandemic of 1918-19, killed 2.5 percent of its victims. With today's world population of 6.4 billion, a flu that virulent would cause 16 million deaths.

Another report, by the Sydney, Australia-based Lowy Institute, says as many as 142 million people around the world could die if bird flu turns into a "worst case" flu pandemic. The institute says global economic losses could run to $4.4 trillion Ñ the equivalent of wiping out the Japanese economy's annual output.

In a worst-case scenario, the report said, the death toll could reach 2 million in the United States.

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History

What history tells us

For instance, in 1957, an Asian influenza pandemic was first identified in the Far East. Immunity to this strain was rare in people less than 65 years of age, and a pandemic was feared in the United States. In preparation, vaccine production began, and health officials increased surveillance for flu outbreaks. Unlike the virus that caused the 1918 pandemic, the 1957 pandemic virus was quickly identified, due to advances in scientific technology. There were a few small outbreaks in the United States, especially among the very young and very old. But later in the year and early into 1958, a "second wave” occurred among the elderly. When the outbreak was over, about 70,000 people in the United States had died. In comparison, about 36,000 die every year from the seasonal flu.

In 1968, the Hong Kong influenza was deadly mainly to those over age 65. The number of deaths between September 1968 and March 1969 for this pandemic was 33,800, making it the mildest pandemic in the 20th century.

In 1976, the swine flu was first identified at Fort Dix and labeled the "killer flu." Experts were extremely concerned because the virus was thought to be related to the Spanish flu virus of 1918. The concern that a major pandemic could sweep across the world led to a mass vaccination campaign in the United States. In fact, the virus — later named "swine flu" — never moved outside the Fort Dix area. Research on the virus later showed that if it had spread, it would probably have been much less deadly than the Spanish flu.

In 1977, the Russian flu viruses were isolated in northern China, spread rapidly and caused epidemic disease in children and young adults worldwide. The 1977 virus was similar to other such viruses that had circulated prior to 1957. And because of the timing of the appearance of these viruses, persons born before 1957 were likely to have been exposed to these viruses and to have developed immunity against them. Therefore, when the virus reappeared in 1977, many people over the age of 23 had some protection against the virus, and it was primarily younger people who became ill from these infections. By January 1978, the virus had spread around the world, including the United States. Because illness occurred primarily in children, this event was not considered a true pandemic. Vaccine containing this virus was not produced in time for the 1977-78 season, but the virus was included in the 1978-79 vaccine.

In 1997 and 1999, there were other avian flu scares. In 1997, at least a few hundred people became infected with the avian A/H5N1 flu virus in Hong Kong, and 18 people were hospitalized. Six of the hospitalized persons died. To prevent the spread of this virus, all chickens (approximately 1.5 million) in Hong Kong were slaughtered. The avian flu did not easily spread from one person to another, and after the poultry slaughter, no new human infections were found.

In 1999, the avian flu virus was found and caused illnesses in two children in Hong Kong. Although both of these viruses have not gone on to start pandemics, their continued presence in birds, their ability to infect humans, and the ability of influenza viruses to change and become more transmissible among people is an ongoing concern.

Experts say the threat of the current avian flu is still serious, with WHO reporting that even a mild pandemic could kill 1.4 million people and cost $330 billion. Another report, by the Sydney, Australia-based Lowy Institute, says as many as 142 million people around the world could die if bird flu turns into a "worst-case" flu pandemic.

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Impact

To prepare, the national government is balancing safety with streamlining to develop vaccines.

Schools, colleges and universities will have to decide whether and how to close for extended periods. University faculty may put more courses online. Institutions that provide student housing will need a plan to feed students who no longer can go to dining halls if mass gatherings are banned.

Businesses will need to prepare for absenteeism - expected to peak at 40 percent - but also strongly discourage people who are sick or exposed from coming to work.

Hospitals are assessing supplies of medicines and masks, beds and health-care providers.

Communities must consider how to recruit and use volunteers to keep essential services running.

It is expected that those who becomes ill but survive the first wave may be immune in a second or third wave, and their services would be in high demand. Altogether, the prediction is that three expected waves would be spread over 18 months.

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