WASHINGTON — The alarm sounded with two sneezy children in California in April. Just five months later, the never-before-seen swine flu has become the world’s dominant strain of influenza, and it’s putting a shockingly younger face on flu.
So get ready. With flu’s favorite chilly weather fast approaching, we’re going to be a sick nation this fall. The big unknown is how sick. One in five people infected or a worst case — half the population? The usual 36,000 deaths from flu or tens of thousands more?
The World Health Organization predicts that within two years, nearly one-third of the world’s population will have caught it.
“What we know is, it’s brand new and no one really has an immunity to this disease,” Health and Human Services Secretary Kathleen Sebelius says.
A lot depends on whether the swine flu that simmered all summer erupts immediately as students crowd back into schools and colleges — or holds off until millions of vaccine doses start arriving in mid-October.
Only this week do U.S. researchers start blood tests to answer a critical question: How many doses of swine flu vaccine does it take to protect? The answer will determine whether many people need to line up for two flu shots — one against swine flu and one against the regular flu — or three.
The hopeful news: Even with no vaccine, winter is ending in the Southern Hemisphere without as much havoc as doctors had feared, a heavy season that started early but not an overwhelming one. The strain that doctors call the 2009 H1N1 flu isn’t any deadlier than typical winter flu so far. Most people recover without treatment; many become only mildly ill.
Importantly, careful genetic tracking shows no sign yet that the virus is mutating into a harsher strain.
We’re used to regular flu that, sadly, kills mostly grandparents. But the real shock of swine flu is that infections are 20 times more common in the 5- to 24-year-old age group than in people over 65. That older generation appears to have some resistance, probably because of exposure decades ago to viruses similar to the new one.
Worldwide, swine flu is killing mostly people in their 20s, 30s and 40s, ages when influenza usually is shrugged off as a nuisance.
Especially at risk are pregnant women. So are people with chronic conditions such as asthma, diabetes, heart disease and neuromuscular diseases including muscular dystrophy.
Still, some of the people who’ve died didn’t have obvious health risks.
“People who argue we’re seeing the same death rates miss the point — they’re in young adults. To me, that shouldn’t happen,” said one infectious disease specialist, Dr. Richard P. Wenzel of Virginia Commonwealth University. He spent the past few months visiting South American hospitals to help gauge what the Northern Hemisphere is about to face.
Panicked crowds flooded India’s hospitals in August after a 14-year-old girl became that country’s first death. In the U.S., regular flu kills 80 to 100 children every winter, and the Centers for Disease Control and Prevention has reports of about three dozen child deaths from swine flu.
Even if the risk of death is no higher than in a normal year, the sheer volume of ill youngsters means “a greater than expected number of deaths in children is likely,” said Dr. Anne Schuchat, director of the CDC’s National Center for Immunization and Respiratory Diseases. “As a society, that’s something that’s much harder for us.”
Swine flu quietly sickened hundreds in Mexico before U.S. researchers stumbled across two children in San Diego who had the same mystery illness. A world already spooked by the notorious Asian bird flu raced to stem the spread of this surprising new virus. Mexico closed schools and restaurants, and barred spectators from soccer games; China quarantined planeloads of tourists. But there was no stopping the novel H1N1 — named for its influenza family — from becoming the first pandemic in 41 years.
Well over 1 million Americans caught swine flu in spring and summer months when influenza hardly ever circulates; more than 500 have died.
In July, England was reporting more than 100,000 infections a week.
Argentina gave pregnant women 15 paid days off last month at the height of its flu season, hoping that staying home would prove protective.
In Saudi Arabia, people younger than 12 and older than 65 are being barred from this November’s hajj, the pilgrimage to holy cities that many Muslims save up their whole lives to make.
And in Australia — closely watched by the U.S. and Europe as a predictor for their own coming flu seasons — hospitals set up clinics outside the main doors to keep possible flu sufferers from entering and infecting other patients.