Severe flu season not of pandemic proportions

By Rob Stein
The Washington Post

	CUAUHTEMOC BELTRAN / AP Karen Terrazas, 7, covers her eyes and holds on to her mother's arm as Karen Howington, a nurse with Imperial County Health Services, prepares to administer a flu shot last week in El Centro, Calif.
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WASHINGTON — While the start of this year's flu season has been especially wretched, flu experts say it is not the killer pandemic they have been worrying about for years. They are much more anxious about a little-noticed case that emerged last week in Hong Kong, where a 5-year-old boy was infected with a bird flu virus.

The child recovered, and no one else appears to have been infected. But experts say they are monitoring the situation closely because whenever a new animal flu virus infects a person it has the potential to create an entirely new virus that could spark a long-feared global cataclysm.

"Every transmission of an avian influenza virus to humans raises the possibility for a pandemic. So we immediately have a red alert," said Klaus Stohr, a top flu specialist at the World Health Organization (WHO) in Geneva. "The concern is that a new virus with high transmissibility and high pathogenicity could emerge."

The Hong Kong boy's family is in isolation, and officials are awaiting results of tests on them and other children who attend the same kindergarten for signs that the virus had spread or mutated.

As soon as WHO officials learned of the case, the agency issued a global alert for scientists to be on the lookout for any flu cases caused by viruses that could not be identified, and they rushed samples of the virus to laboratories to begin deciphering its genetic code and developing tests that could identify it quickly if it were to spread.

"We have to treat it seriously," Stohr said. "Fortunately, so far it looks like an isolated case with no human-to-human transmission. But we are concerned."

In the United States, the federal Centers for Disease Control and Prevention (CDC) responded by issuing an advisory to scientists to watch for any unusual flu viruses and ship them immediately to Atlanta for analysis. None has been found.

"As opposed to what we're seeing with this year's flu season, which is, granted, a bad season, what we're concerned about is the beginning of a pandemic of influenza with a new virus that emerges from the animal population," said Scott Harper, a CDC flu expert. "This would be really an entirely different scenario than just having a bad influenza season."

The flu outbreak under way in the United States and Europe is caused primarily by the Fujian virus, first detected in the Fujian province of China last year. Part of the reason officials believe this year's flu season will be more severe than in recent years is that the Fujian virus is from a family of flu viruses known as H3N2, which tend to be more likely than other viruses to cause widespread illness.

The Fujian strain is the result of a slight genetic change that occurred to an H3N2 virus that has been circulating for years. That means people's immune systems have not been exposed to that precise virus previously, making them more susceptible to infection. Because it was discovered too late to be included in this year's vaccine — although a close relative was included — the vaccine probably is not as protective as it has been in past years.

But most people have had at least some exposure to other H3N2 viruses, making it likely that their immune systems have some power to protect against them.

In contrast, the virus that infected the Hong Kong youngster comes from a family of flu viruses known as H9N2, which usually infect only birds. Most people's immune systems offer no protection from the virus.

Experts warn that a pandemic is coming, it's just a question of when.

"It's going to happen," said Dr. Greg Poland of the Mayo Clinic. "For the American public in particular, I think it will be horrific."

By historical pattern, Poland said it's about time for the next one. There have been three in the past 100 years — in 1918, 1957 and 1968.

The WHO has estimated that the next pandemic is likely to send 1 million to 2.3 million people to the hospital and kill 280,000 to 650,000 in industrialized nations alone. Its impact probably will be greatest in developing countries.

Animal flu viruses jump to humans on a regular basis. Most of the time they do not cause major outbreaks because they are not well-suited to humans — they cannot spread easily among people or do not make people very sick.

But animal flu viruses periodically combine with a human virus and produce a hybrid that spreads easily among people and makes them very sick. That is what is believed to have occurred in 1918-19, when the "Spanish flu" caused a global pandemic that killed perhaps 40 million people.

"The virus has to be capable of spreading well in humans. If it's not able to do that, it will stop spreading in the human population. If it is able to do that, you'll have a pandemic," the CDC's Harper said. "That's why whenever we hear about one of these cases, we get concerned."

Information on past flu pandemics was provided by The Associated Press.

Copyright © 2003 The Seattle Times Company