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LONDON – For men with fertility problems, some doctors are prescribing a very conventional way to have a baby: more sex.
In a study of 118 Australian men with damaged sperm, doctors found that having sex every day for a week significantly reduced the amount of DNA damage in their patients’ sperm. Previous studies have linked better sperm quality to higher pregnancy rates.
The research was announced Tuesday at a meeting of the European Society of Human Reproduction and Embryology in Amsterdam.
Dr. David Greening of Sydney IVF, a private fertility clinic in Australia, and colleagues looked at 118 men who had damaged sperm. Greening and colleagues told the men to have sex every day for a week. After seven days, the doctors found that in 81 percent of the men, there was a 12 percent decrease in the amount of damaged sperm.
Many fertility experts suggest men abstain from sex before their partners have in-vitro fertilization, to try to elevate their sperm counts.
Sperm quality can also be improved if men don’t smoke, drink moderately, exercise, or get more antioxidants.
Since concluding the study, Greening says he now instructs all couples seeking fertility advice to start by having more sex. “Some of the older men look a little concerned,” he said. “But the younger ones seem quite happy about it.”
Experts think sex helps reduce the DNA damage in sperm by getting it out of the body quickly; if sperm is in the body for too long, it has a higher chance of getting damaged.
Some experts said that while Greening’s research is promising, it doesn’t prove that daily sex for men with fertility problems will actually produce more babies.
Greening said he and his colleagues are still analyzing the study data to determine how many women got pregnant.
“Looking at sperm DNA is just one part of the puzzle,” said Bill Ledger, a professor of obstetrics and gynecology at the University of Sheffield, who was not connected to the research. “Maybe this will improve pregnancy rates, but we still need to do more studies.”
Ledger said instructing couples with infertility problems to have more sex could stress their relationship. “This may add even more anxiety and do more harm than good,” he said. He said couples shouldn’t feel pressured to adjust their sex lives just for the sake of having a baby.
Greening said the study’s findings were ultimately very intuitive. “If you want to have a baby, our advice is to do it often.”
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ATLANTA – In a startling measure of just how widely a new disease can spread, researchers accurately plotted swine flu’s course around the world by tracking air travel from Mexico.
The research was based on an analysis of flight data from March and April last year, which showed more than 2 million people flew from Mexico to more than 1,000 cities worldwide. Researchers said patterns of departures from Mexico in those months varies little from year to year; swine flu began its spread in March and April this year.
Passengers traveled to 164 countries, but four out of five of those went to the United States. That fits with the path of the epidemic a year later. The findings were reported Monday in the New England Journal of Medicine.
The research shows promise in forecasting how a new contagion might unfold, indicated one government health official who praised the work.
“We share a common interest in this issue: If we map the global airline distribution network, can we anticipate, once a virus emerges, where it is likely to show up next?” asked Dr. Martin Cetron of the U.S. Centers for Disease Control and Prevention. He leads CDC’s division of global migration and quarantine.
The new swine flu virus was first reported in the United States in mid-April, but the first large outbreak was in Mexico at about the same time. Health officials believe cases of the new virus were circulating in Mexico in March.
Scientists have long assumed a relationship between air travel and spread of the virus. But the new research for the first time confirmed the relationship, said Dr. Kamran Khan, who led the study. He is a researcher at St. Michael’s Hospital in Toronto.
For years, Khan and his colleagues have been working on a system to use air travel information quickly to determine how a new contagion is likely to spread around the world.
Their data sources include the International Air Transport Association, an international trade association representing 230 airlines and the vast majority of scheduled international air traffic.
The study showed the majority of passengers flew to the United States, with Canada a distant second and France a more distant third.
More than 90 percent of the time, Khan and his colleagues accurately matched air traffic volumes to which countries did and did not suffer swine flu outbreaks as a result of air traffic.
The top 11 destination cities from Mexico were all in the United States. Los Angeles was the leader, receiving about 9 percent of all passengers from Mexico, and New York City was second, with about 5 percent.
In contrast, the only South American entry in the top 40 destination cities was Buenos Aires, at No. 22. Passengers were even fewer when it came to cities in neighboring Guatemala and other Central American countries.
The data show not only how disease spreads out of Mexico, but also that air travel is mainly among more industrialized countries, experts said.
A second study released by the journal found a sharp rise in pneumonia cases in non-elderly Mexicans from late March to late April. Normally, only about a third of severe pneumonia cases in Mexico are in people ages 5 to 59. But during the recent swine flu outbreak, more than 70 percent were in that younger age group.
The study seems to support plans to target swine flu prevention efforts to the young, experts said.
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WASHINGTON (AFP) – President Barack Obama on Saturday urged his fellow Americans to get tested for HIV in an effort to reduce transmission of the virus that causes AIDS.
“On this 14th commemoration of National HIV Testing Day, I urge Americans to take control of their own health — and protect those they love — by getting tested for HIV and working to reduce HIV transmission,” Obama said in a statement.
“While its impacts are not evenly spread — infection rates are particularly high among gay and bisexual men, African Americans and Latinos — when one of our fellow citizens becomes infected with HIV every nine-and-a-half minutes, the epidemic affects all Americans,” he said.
Obama noted that of the estimated 1.15 million people infected with HIV in the United States, more than 230,000 — one in five — do not know they are infected.
The US president last month unveiled a plan to commit 63 billion dollars over six years to battle chronic global health crises, including AIDS, malaria and tuberculosis, a continuation of a landmark initiative launched by his predecessor George W. Bush.
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WASHINGTON (Reuters) – Drug manufacturers will offer some $80 billion in prescription discounts for Medicare recipients under a deal unveiled on Saturday, which could boost President Barack Obama as he pushes to overhaul the $2.5 trillion U.S. healthcare system.
“The agreement reached today to lower prescription drug costs for seniors will be an important part of the legislation I expect to sign into law in October,” Obama said in formally announcing the pact.
The companies have agreed to provide for the next decade a 50 percent discount for those elderly and disabled Americans in the Medicare health insurance program who face a gap in coverage after their drug costs reach a certain level, known as the “doughnut hole”.
“The existence of this gap in coverage has been a continuing injustice that has placed a great burden on many seniors,” Obama said in a statement. Medicare coverage does not apply to payments between $2,700 and $6,154.
The deal was negotiated between the Pharmaceutical Research and Manufacturers of America industry association and Senate Finance Committee Chairman Max Baucus who is leading one of many congressional panels drafting healthcare legislation.
“This commitment to support legislation that will help close the coverage gap reflects our ongoing work with Congress and the Administration to make comprehensive health care reform a reality this year,” the industry group said in a statement.
UNINSURED AMERICANS
Costs for healthcare have soared faster than the inflation rate and the Democratic president has pledged to work to curb those costs as well as find a way to provide coverage to the 46 million uninsured Americans.
Americans strongly support fundamental changes to the healthcare system and a move to create a government-run insurance plan to compete with private insurers, according to a New York Times/CBS News poll published on Saturday.
The White House has said some $950 billion in cuts have been found to cover its reform efforts but there are reports that the costs could reach as much as $1.6 trillion and still not cover everyone, setting off a fierce debate on how to close the gap.
That has given Republicans an opening to attack, particularly since Americans are growing worried about the eye-popping record budget deficits facing the country — more than $1.8 trillion in fiscal 2009 alone.
Democrats in the U.S. House of Representatives proposed a draft of their healthcare bill on Friday that calls for all citizens to be able to get insurance regardless of medical history and that coverage should be mandatory for individuals and businesses.
They would create a new government plan to help cover the uninsured — a move backed by Obama but resisted by Republicans and some centrist Democrats who fear it will overwhelm private insurers and require vast amounts of public funding.
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OTTAWA (AFP) – A Canadian federal court on Thursday upheld pharmaceutical giant Pfizer’s patent for Viagra, dashing generic drug maker Novopharm’s longing for sales of cheaper erection drugs.
Judge Michael Kelen said in his decision that Novopharm failed to demonstrate the Pfizer patent was invalid.
He ordered Canada’s health minister not to grant the generic drug maker’s request for special permission to manufacture a Viagra knock-off until the Pfizer patent expires in 2014.
Pfizer had filed the application to prohibit Novopharm from introducing a generic version of the hugely popular drug.
Sildenafil, the key ingredient in Viagra, was initially developed by Pfizer in the mid-1980s as one of a number of compounds for the treatment of hypertension and angina.
Angina patients unexpectedly experienced erections while being treated with sildenafil to lower their blood pressure, and so it was marketed to treat erectile dysfunction.
In its submissions, Novopharm, a subsidiary of the world’s largest generic drug-maker Teva Pharmaceutical, questioned the timing of patent filings around Pfizer’s discovery of the active ingredient in Viagra.
But in his decision, Judge Kelen said: “The court concludes that the applicants have met their legal burden to establish the validity of the patent.”
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WASHINGTON – It may be riskier on the lungs to smoke cigarettes today than it was a few decades ago — at least in the U.S., says new research that blames changes in cigarette design for fueling a certain type of lung cancer.
Up to half of the nation’s lung cancer cases may be due to those changes, Dr. David Burns of the University of California, San Diego, told a recent meeting of tobacco researchers.
It’s not the first time that scientists have concluded the 1960s movement for lower-tar cigarettes brought some unexpected consequences. But this study, while preliminary, is among the most in-depth looks. And intriguingly it found the increase in a kind of lung tumor called adenocarcinoma was higher in the U.S. than in Australia even though both countries switched to so-called milder cigarettes at the same time.
“The most likely explanation for it is a change in the cigarette,” Burns said in an interview — and he cited a difference: Cigarettes sold in Australia contain lower levels of nitrosamines, a known carcinogen, than those sold in the U.S.
That’s circumstantial evidence that requires more research, he acknowledged.
But anti-smoking advocates are citing the study as Congress considers whether the Food and Drug Administration should regulate tobacco, legislation that would give the agency power to decide such things as whether to set caps on certain chemicals in tobacco smoke.
Smokers once tended to get lung cancer in larger air tubes, particularly a type named “squamous cell carcinoma.” Then doctors noticed a jump in adenocarcinoma, which grows in small air sacs far deeper in the lung. Initial studies blamed introduction of filtered, lower-tar cigarettes. When smokers switched, they began inhaling more deeply to get their nicotine jolt, pushing cancer-causing smoke deeper than before.
Burns’ study, presented at a meeting of the Society for Research on Nicotine and Tobacco, took a closer look. He compared smoking behaviors of different age groups over four decades — how much they smoked, when they started, when they quit — and how cancer-risk changed.
The risk of squamous cell carcinoma stayed about the same over those years, Burns found. But adenocarcinoma rose. It makes up 65 percent to 70 percent of newly occurring U.S. lung cancer cases, but no more than 40 percent of Australia’s lung cancer, he said.
While the nation’s total lung cancer cases have inched down as the number of smokers has dropped in recent years, the study suggests an individual smoker’s risk of getting cancer is higher.
It’s well known that cigarettes differ from country to country, because of different tobacco crops grown locally and smokers’ varying tastes. Nitrosamines are a byproduct of tobacco processing and levels vary for several reasons, including differences in curing practices.
Australian cigarettes contain about 20 percent of the nitrosamine content of U.S. cigarettes, making the chemical a prime suspect, concluded Burns, who has been scientific editor of several surgeon general reports on tobacco.
That doesn’t rule out a role for deeper inhaling, cautioned Dr. Michael Thun of the American Cancer Society: “There’s several strong suspects in the lineup. They may have acted in combination.”
Philip Morris USA spokesman David Sutton called the study speculative and hard to evaluate until it’s published in a medical journal, something Burns plans to do.
Still, Philip Morris, which supports FDA tobacco regulation, began taking steps with its growers in 2000 that have yielded “significantly lower” nitrosamine levels in recent years’ supplies, Sutton said.
Be careful in assuming lower-nitrosamine cigarettes are less lethal, said Dr. Neal Benowitz of the University of California, San Francisco, a well-known tobacco expert. Lung cancer is only one of tobacco’s many risks — it causes heart disease and other killer diseases, too.
“If you reduce someone’s (lung cancer) risk by 10 percent, that’s not really meaningful for an individual,” he said. “The goal still is to get them to stop.”
AmericanHealthOptions reminds that Zero Nicotine is one of top smoking cessation aids.
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GENEVA – Dozens of countries urged the World Health Organization to change its criteria for declaring a pandemic, saying the agency must consider how deadly a virus is — not just how far it spreads across the globe.
Fearing a swine flu pandemic declaration could spark mass panic and economic devastation, Britain, Japan, China and others asked the global body on Monday to tread carefully before raising its alert. Some cited the costly and potentially risky consequences, such as switching from seasonal to pandemic vaccine, even though the virus so far appears to be mild.
Although no formal changes were made Monday, WHO said it would listen to its members’ requests.
“It’s certainly something we will look at very closely,” said Dr. Keiji Fukuda, WHO’s flu chief.
The alert for swine flu is now at phase 5, which means the virus is spreading unchecked inside at least two countries in a single region. Under the existing rules, phase 6 indicates outbreaks in at least two different regions of the world and that a pandemic is under way.
“We need to give you and your team more flexibility as to whether we move to phase 6,” Britain’s Health Secretary Alan Johnson told WHO Director-General Dr. Margaret Chan, a public health veteran who has made combatting the outbreak her top priority since the new virus appeared in North America last month.
Chan warned that swine flu could pose a grave threat to humanity even though the fatality rate is low, with 76 known deaths out of 8,829 confirmed cases in 40 countries. That total does not include Greece, which reported its first confirmed case on Monday.
“This virus may have given us a grace period, but we do not know how long this grace period will last,” Chan said. “No one can say whether this is just the calm before the storm.”
Japan reported the largest jump from just four cases over the weekend to more than 170 cases, health officials said Tuesday. Most involved teenagers who had not traveled overseas.
Spain and Britain have the highest numbers of cases in Europe, reporting 103 and 101 cases, respectively.
A pandemic announcement would likely have severe economic consequences: It could trigger expensive trade and travel restrictions such as border closures, airport screenings and quarantines.
Governments also fear mass panic, social disruption and overwhelmed health systems. Extraordinary measures such as large-scale pig slaughters like the recent one in Egypt could be taken, even if they aren’t scientifically justified.
Mexico, which has suffered the most deaths and virtually shut down its economy for several days in response to the outbreak, urged WHO to reconsider its pandemic scale.
“People don’t understand what 4, 5 or 6 means,” Mexico’s Health Minister Jose Angel Cordova told reporters. “They think that when you go to a higher level things are worse.”
U.S. Health and Human Services Secretary Kathleen Sebelius told The Associated Press she wanted more information on the proposal before taking a position, but she was impressed how many countries supported it. Still, in a speech to the assembly she noted that each day 26,000 children will die from poverty and preventable diseases. Swine flu is a long way from causing that kind of devastation.
So far the virus appears to be mild, though scientists are concerned that many of the more severe symptoms have turned up in younger people, especially in Mexico. Flu is normally most dangerous to babies and the elderly.
WHO chief Chan noted that the disease could combine with other flu strains, including the lethal H5N1 bird flu virus which hasn’t spread much among humans.
The signal for starting pandemic vaccine production has yet to be given, but it is essential that countries use their stockpiles of drugs wisely, she said. WHO has said two anti-viral drugs, Tamiflu and Relenza, have been effective against the new swine flu.
“It is absolutely essential that countries do not squander these precious resources through poorly targeted measures,” Chan said.
Chan and U.N. Secretary-General Ban Ki-moon are scheduled to meet with senior representatives of pharmaceutical companies Tuesday to discuss the vaccine question. The U.N. declined to name the companies but major vaccine producers include Sanofi-Aventis, GlaxoSmithKline and Baxter International.
Key issues include: how soon can a pandemic vaccine be produced, and how much of it will be available to each country. Many governments, including Britain, have already signed large advance orders, potentially depriving poorer countries of a chance to buy their own stock.
AmericanHealthOptions reminds that most common medication for fighthing against swine flu is Tamiflu.
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The recession might be a little less painful for some Americans, who won’t lose their prescription medications if they lose their jobs.
Pfizer Inc. said Thursday it will give away more than 70 of its most widely prescribed drugs, including Lipitor and Viagra, for up to a year to people who have lost jobs since Jan. 1 and have been taking the drug for three months or more. The announcement comes as the unemployment rate topped 8.9 percent in April.
Pfizer stands to benefit, too — by keeping its customers, and with a tax write-off that will cover much of the cost of the donations. The move also buys the world’s largest drugmaker some good will as Washington looks to overhaul the health care system.
“Everybody knows now a neighbor, a relative who has lost their job and is losing their insurance. People are definitely hurting out there,” Dr. Jorge Puente, Pfizer’s head of pharmaceuticals outside the U.S. and Europe, told The Associated Press in an exclusive interview Wednesday. “Our aim is to help people bridge this point.”
The 70-plus drugs covered in the program include several diabetes drugs and some of Pfizer’s top money makers, from cholesterol fighter Lipitor and painkiller Celebrex to fibromyalgia treatment Lyrica and Viagra for impotence. Also included are some antibiotics, antidepressants, heart medications, contraceptives and smoking cessation products. Cheaper generic versions are available for most of the drugs.
The program will likely help prevent patients from switching to cheaper brands or generics through the worst of the recession and could help retain those taking top-seller Lipitor, which will begin competing with generic versions next year.
The giveaway was heralded by some as a brilliant marketing move that will generate low-cost publicity, build consumer loyalty and keep inventory from piling up.
“What are the alternatives? To slow down manufacturing operations?” asked WBB Securities analyst Steve Brozak. “This is going to go down as a Harvard Business School textbook example of what to do with product when you can’t sell it.” Pfizer, among other drugmakers, has seen sales fall for many drugs as people cut spending, even for essentials such as health care.
The 10 best-selling drugs included in the program accounted for more than $26 billion, or 64 percent, of Pfizer’s total sales last year. Officials for New York-based Pfizer said they don’t know how much the program will cost and haven’t put a cap on spending for it.
Brozak said the cost would surely be far less than a national marketing campaign, which can run hundreds of millions of dollars annually.
The cost will be defrayed by tax deductions. Companies that donate inventory can deduct their cost to make the product plus one-half the difference between their cost and the selling price from their taxable income. Pfizer is running the program through its charitable foundations.
“At this point it’s too early to consider the benefit from this program,” company spokesman Christopher Loder said. “But that’s not the reasons we’re doing this. We’re doing this because patients are in need.”
Many drugmakers, including Pfizer, have been raising prices, partly to offset declines in revenue as the global recession reduces the number of prescriptions people can afford.
But companies in other industries have recently offered to help laid-off customers. In February, Hyundai Motor Co. guaranteed it would temporarily make car payments for people who lost their jobs, and Ford Motor Co. and General Motors followed shortly after.
Drugstore operator Walgreen is offering free in-store clinic visits to the unemployed and uninsured for the rest of the year. And men’s clothing retailer JoS. A. Bank Clothiers Inc. has offered to refund the price of a suit if the buyer loses his job.
Pfizer said the idea for the program came just five weeks ago at a leadership training meeting as workers discussed how a lot of patients are struggling.
Puente said he urged top management to approve the program, presenting a recent Associated Press article about how newly uninsured diabetics are suffering serious complications because they can no longer afford the medicines and testing supplies. Approval came quickly.
“It was my idea,” he said. “I floated it, and the reception it got was so dramatic that it very quickly became our idea.”
Colleagues suggested employees could donate to a fund to help support the effort, Puente said. He said some workers had tears in their eyes when discussing how they could help people who had lost jobs.
Applicants will have to sign a statement that they are suffering financial hardship and provide a “pink slip” or similar employer notice.
Patients can call a toll-free number, 866-706-2400, to sign up, and those whose drugs are not included in the program will be referred to other company aid programs. Starting July 1, patients can also apply online at http://www.PfizerHelpfulAnswers.com, which has information about the other aid programs.
Applications will be accepted through Dec. 31, with medication provided for up to 12 months after approval — or until the person becomes insured again.
Pfizer and the rest of the drug industry are trying to have a voice in the debate over how to overhaul the U.S. health care system, partly by joining in a pledge this week to help hold down inflation of health costs.
“There’s a long-term benefit there, beyond the good will and the publicity,” said David Heupel, health care portfolio manager at Thrivent Large Cap Growth Fund. “Pfizer is trying to maintain their (market) share, if not grow their share” by keeping people from switching to generic versions of its drugs to save money.
“If you’re already taking medication that’s working, typically doctors don’t push to change it,” Heupel said.
Pfizer said that from 2004 through 2008, its patient assistance programs helped 5.1 million people get 51 million Pfizer prescriptions for free or at reduced cost, with a total value of $4.8 billion.
Earlier this year, rival Merck broadened the eligibility for its own assistance program to people with a household income below $88,000 for a family of four with no insurance, among other qualifiers. Previously it was $44,100. The program has been in place for about 50 years.
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NEW YORK (Reuters Health) – Women who suffer from depression after giving birth can often be helped with antidepressants, and when treatment is successful it usually improves sexual problems.
In the Journal of Clinical Psychiatry, Dr. Katherine L. Wisner, of the University of Pittsburgh Medical Center, Pennsylvania, and colleagues report their assessment of sexual problems in women diagnosed with postpartum depression. The information was drawn from an 8-week study comparing the antidepressants nortriptyline (for example, Sensoval, Aventyl) and sertraline (Zoloft, Lustral) for postpartum depression in 70 women.
At the start of the study, 73 percent of women reported problems in at least three areas of sexual function. By week 8, this number had fallen to 37 percent, and women whose depression resolved were more likely to report fewer concerns about sex drive, sexual arousal, and reaching orgasm than those whose depression did not remit, regardless of which antidepressant they received, according to the researchers.
The investigators point out that for new mothers with depression and sexual problems, prior research has shown that recovery depends not only on relieving the depression but also on the time it takes for tissues around the vagina to recover from the stress of childbirth.
In the current study, however, the decrease in sexual concerns was specifically linked with improvements in depression rather than with the passage of time, according to the article.
The lack of a specific association with either nortriptyline or sertraline suggests that it does not matter how the depression is addressed, only that it is relieved, the authors note.
SOURCE: Journal of Clinical Psychiatry, March 2009.
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WASHINGTON – A flu virus is a powerhouse of evolution, mutating at the maximum speed nature allows. A mild virus can morph into a killer and vice versa.
One change already made this year’s swine flu more of a problem, helping it spread more easily among people. The big question is: What mutations are next? That’s why scientists are watching it so closely.
“There are no rules to flu viruses; they are just so mutable,” said Dr. Paul Glezen, a flu epidemiologist at the Baylor College of Medicine in Houston. “The fact that it changes all the time really confounds our efforts to control it.”
Think of flu’s evolution like a family tree: In the current flu’s distant ancestry are last century’s three pandemics. But its more immediate relatives are swine flu strains that were no big deal to humans.
The good news right now is that this flu has lost some of the most dangerous genetic traits of past pandemics. The bad news is that it’s gained something its parents didn’t have: the ability to spread from human to human.
Flu reproduces about every eight hours, said Dr. Raul Rabadan, professor of computational biology at Columbia University. That means this morning’s flu is a parent by the afternoon, a grandparent by the evening, and a great-grandparent by the next day.
Instead of complex double-helix DNA — nature’s basic biological instruction book — flu has a simpler, single strand of genetic code. Normal DNA has a spellcheck-like system that reduces mistakes in replicating the code; the flu virus does not. So mutations come more often. If the mutations are good for the virus, they multiply, and voila, you have a new and sometimes nastier flu.
Scientists are trying to piece together swine flu’s ever-changing genome, its genetic ancestors and the random mutations that in this instance turned a simple pig disease into something that scares billions.
They also don’t know how the virus is going to mutate next.
In the world’s most devastating global flu epidemic in 1918, the first wave of cases in the spring were mild. Then, the virus evolved and came back in the fall as a strain that proved truly deadly, flu experts say. So scientists today are watching to see if that could happen again.
Also troubling is the possibility that this virus could develop resistance to anti-flu drugs, and flu trackers are watching for such changes, Centers for Disease Control and Prevention flu chief Dr. Nancy Cox said.
It’s impossible to know where this swine flu strain began exactly, Cox said. But flu trackers do have clues to its closest ancestral genes.
“Its two parents were swine viruses that we know and love,” said virologist Dr. Richard Webby, a researcher at St. Jude Children’s Research Hospital in Memphis, Tenn.
The mother of the swine flu was a surprising genetic event that went unnoticed except by a few scientists a little over a decade ago. Three influenza strains — some pig, some bird, some human — combined in pigs to form two new strains of swine flu. This new flu was unusual. Virus hunters called it a “triple reassortment.”
That 1998-99 flu in pigs first hit a farm in North Carolina, then spread to Iowa, Texas, Oklahoma and eventually to at least 23 states. No more than 4 percent of the swine died. But the disease was in more than one-quarter of tested pigs. A handful of people who were in close contact with the hogs got slightly sick when they caught this flu from pigs, but they didn’t die and didn’t spread it to others.
In 2005, a 17-year-old Wisconsin boy caught that triple reassortment flu virus from “respiratory secretions” of a pig he had been helping his brother-in-law butcher, according to the CDC. He recovered and didn’t pass it on to others.
There have been about 10,000 generations of that virus since. Six of the eight genetic segments of the current swine flu can be traced to that triple combination, Rabadan said.
The rest of the swine flu parentage is more of a mystery. The other two of the eight genetic segments can be traced to pig viruses in Europe and Asia that were seen from time to time in the 1990s, Rabadan said. Scientists don’t quite know if those other two segments combined with the triple reassortment at the same time or separately.
How the triple reassortment genes and the European and Asian genes met and mixed is not known, Webby said.
The three global flu epidemics of the past, including the 1918 event, all passed on traits to ancestors of this flu, Rabadan said. But there have been many changes in the thousands of generations since.
A specific gene for virulence that was seen in the 1918, 1957 and 1968 pandemics was notably absent in this swine flu, said Dr. Peter Palese, a prominent flu researcher for Mount Sinai Medical Center in New York. He said when he removed that gene from other viruses of the past, they weren’t as dangerous.
Rabadan suggests the way to think of this flu is like a homemade car with parts from different vehicles. The parts have all been in several different vehicles before. Sometimes the combination of parts is a dud and the car doesn’t move. And sometimes you get a race car. A pandemic is a race car.
All eight of the new flu’s genetic segments have been in different viruses before. But this is the first time this specific combination has been seen. The big question is: Why is this particular swine virus spreading so fast among people when past swine viruses haven’t?
One possibility is that it’s just this particular combination of the eight parts that makes it spread among people, Webby said. But a more logical explanation is that a small mutation within the individual genetic segments changed things.
These tiny changes are possible because there are about 13,000 individual letters, or bases, in the flu genetic code, Rabadan said. That’s tiny compared to more than 3 billion in humans.
One prime suspect is the surface protein hemagglutinin, the “H” in the virus’ H1N1 name. It is “probably the most important gene determining virulence and immunological characteristics,” according to Palese.
In flu viruses, scientists have so far identified 16 hemagglutinins. Only three — H1, H2 and H3 — commonly infect humans. The other surface protein, neuraminidase, has nine variations. Palese said scientists are seeing more different types of flu strains because of better surveillance and increases in bird, pig and human populations.
“These genetic processes of mutation and genetic reassortment occur all the time,” he said, “and every once in a time, it’s a lottery winner.”
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