Scientists tackle many H1N1 questions

The Dallas Morning News

DALLAS — Top headlines about the H1N1 flu virus continue to be about the lack of vaccine. But behind the news is a daily trickle of new information about the virus itself.

Since H1N1, commonly known as swine flu, was first spotted in the spring, thousands of researchers all over the world have been tweezing out the secrets of the pandemic. What they’ve found is now showing up in science journals, often available on Web sites weeks before publication of the paper version.

The trickle is fast becoming a flood, with more reports issued daily. What do we know now that we didn’t know when the first swine flu warnings were sounded in April?

The best news is that it could be a lot worse. Flu experts have been expecting and dreading a pandemic for several years.

“It was always anticipated that we would see an easily transmitted and highly virulent organism,” said Dr. Patrick Brennan, chairman of the federal Healthcare Infection Control Practices Advisory Committee. “We are seeing half of that picture.”

That has meant that although swine flu spreads easily, most people who get it suffer no more than a few days. But that’s little solace for the relatively few who get very, very sick.

Here are some answers to H1N1 questions, based on the science of the moment:

Q. Why is the vaccine production going so slowly?

A. The manufacturers had bad luck when there was no room for a misstep, said Dr. James Luby, an expert on infectious diseases at the University of Texas Southwestern Medical Center. He’s been studying nasty microbes at UT Southwestern since 1967.

Making flu vaccine, Luby said, requires growing the virus in chicken eggs. Some strains, even of the same kind of flu, grow faster than others.

For the seasonal flu, manufacturers may have time to adjust midstream. But the need to get the H1N1 vaccine out in a hurry meant that researchers had to take their best shot. The strain that was chosen simply grows more slowly in vaccine production than most other flu viruses.

“I think we did the best that we could,” he said.

Q. Are we near the peak of this infection?

A. Nobody knows. What flu experts are really worried about is whether there will be another peak. In the 1917-1918 and 1957-1958 pandemics, illness was widespread in the fall, went away, then came roaring back in January.

This year’s pattern of infection looks a lot like those earlier pandemics, Luby said.

Q If I get the vaccine this year, will it protect me next year?

A. Maybe not, says Dr. Jeffrey Kahn, chief of infectious diseases at Children’s Medical Center in Dallas and professor of pediatrics and microbiology at UT Southwestern.

“Next year’s swine flu vaccine may need to be a different strain than this year’s,” he said.

After all, new seasonal flu vaccines are made every year. The viruses mutate enough to avoid the body’s defenses that had been primed from the prior year’s shot.

So far, H1N1 is not changing. But as more people become immune — either through infection or vaccination — that will put genetic pressure on the virus to change, Kahn said.

Q Why doesn’t this flu follow the same seasonal pattern as most other flus?

A. Scientists don’t really know why any flu has a particular season, so figuring out why this one is different is a real challenge.

Kahn and Luby think the difference has something to do with the fact that very few people had any immunity to this virus. So what might have been a small cluster of off-season infections instead spread like flames in dry tinder.

Why do the elderly seem to have resistance to the new H1N1 flu?

This flu is something like the 1957 pandemic flu. And something like the 1976 swine flu. People who were young adults in 1957 seem to have some resistance to the new flu. People who were around for the 1957 flu and got the 1976 flu vaccine appear to have even more resistance, Luby said.

Q Why do a small number of otherwise healthy people get much sicker than most others who catch this flu?

A. Some of the worst cases are easy to understand: People with other health problems are more vulnerable. The risk to pregnant women is harder to explain, but may be related to hormonal changes to the immune system or breathing constrictions in the third trimester. More mysterious still are the otherwise healthy people who get very ill.

Kahn thinks that some people have a genetic weakness to this particular virus that doesn’t show up in any other way — an invisible pre-existing condition.

Luby blames some of the worst illness on the fact that some people carry colonies of microbes around without any illness. The flu infection damages the lungs and gives otherwise asymptomatic pneumonia and MRSA bacteria a place to grow.

But viruses are too tricky for any pat answer.

“If you take identical twins and expose them to the same virus, sometimes you have very different clinical outcomes,” Luby said.

How many people need to become immune — either from infection or vaccine — before this outbreak will be controlled?

Kahn and Luby agree that at least 60 percent of the population needs to have resistance to confer significant “herd immunity.”

Think of a firebreak where the land has already been burned off so that new sparks find no fuel to ignite.

The current outbreak may infect 20 percent or 30 percent of the population, meaning tens of millions of people will still need the vaccine.

Should you get the vaccine when it becomes available?

“I’m advising my patients to get it when they can,” Luby said.

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WHAT MEDICAL JOURNALS REVEAL

Researchers have been publishing reports about the H1N1 flu in medical journals. Here’s what some of them are writing about:

—The Journal of the American Medical Association recently published a piece about critically ill H1N1 patients in Canada.

—The New England Journal of Medicine has a report on the poor precision of the quick tests in doctors’ offices for the virus.

—Clinics, a Brazilian journal, offers guidelines for treatment used in a large hospital in that country.

—The Indian Journal of Medical Ethics critiques the response to an outbreak in Pune.

—The Pediatric Infectious Disease Journal has an article with the stomach-turning title of “Melting Muscles,” about a condition that afflicted a young H1N1 flu patient, who recovered.

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HOW H1N1 AFFECTS THE BODY

Like all forms of flu, H1N1 is a virus that can quickly multiply inside the body. Here’s how it works:

—Typically, H1N1 is spread person-to-person through coughing or sneezing, like the seasonal flu. Once inside the body, it enters the respiratory system.

—The virus then binds to the surface of a cell, overriding its natural mechanism and ordering the cell to reproduce copies of the virus.

—The new copies of the virus leave the cell, which dies, and the multiplying virus infects other cells. The virus continues to reproduce, and symptoms of the illness emerge. Eventually, the body’s immune system responds to fight it off.

—In its weakened state, the body can be vulnerable to other threats, such as bacterial infections. This is especially the case in children and young adults infected with H1N1.

Sources: Centers for Disease Control and Prevention; howstuffworks.com

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(c) 2009, The Dallas Morning News.

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