Scientists Struggle to Understand Swine Flu Virus
American health officials believe they are getting closer to answering those questions, or, at least, to ruling out wrong-headed theories.
“Weve begun to knock off hypotheses,” said Dr. Scott F. Dowell, director of global disease detection with the U.S. Centers for Disease Control and Prevention.
Among the factors disease detectives have discounted are Mexicos air pollution, secondary infections and poor health care. But they still do not know why so many Mexicans have died, although it could be because many more people actually have had the virus than health officials realize.
In Mexico, the virus is suspected of killing more than 150 people and sickening more than 2,400. Recent information suggests swine flu-related hospital admissions and deaths may have peaked and are declining, but no other country has shown any numbers close to those seen in Mexico.
The only other country to report a swine flu death is the United States, and that involved a toddler from Mexico who was visiting Texas with his family.
The leading theory remains that the virus itself is not significantly different in Mexico, but that the outbreak has for some reason just hit harder there, infecting more people overall. The more people who are infected, the more likely there will be severe cases and even deaths.
When the Mexican health secretary spoke this week about a 6 or 7 percent death rate, his figures were based on the number of deaths divided by the number of suspected infections. But authorities cannot be certain how many people have been infected, especially those who suffered only mild symptoms.
Mexican authorities have not tried to count mild cases, focusing instead on the severely ill and the dead. So the death rate may be much lower than 6 or 7 percent – and probably is, according to some experts.
A 6 to 7 percent death rate would make the Mexican swine flu nearly three times deadlier than the worst flu pandemic in the last 100 years – the 1918 Spanish flu, which killed an estimated 20 million to 50 million people worldwide.
That seems unbelievably high for this new virus, said Richard Webby, a flu researcher at St. Jude Childrens Research Hospital in Memphis.
Webby and others do not believe the swine flu in Mexico is different from whats been seen in U.S. patients. The virus samples in both countries match.
The CDC sent four epidemiologists and one lab scientist to Mexico over the weekend to investigate the disease there, and the agency expects to send a half-dozen more people this week, said Dowell, of the CDC.
- A second infection complicating the flu cases. A common danger in flu is that the patient is co-infected with pneumonia or other bacteria, which can lead to death. But lab tests of 33 Mexican patients, including seven who died, did not find that problem.
- Low-quality health care. CDC investigators have not seen any obvious problem. They have found capable doctors and well-equipped, high-quality hospitals, Dowell said.
- A medicine is compounding the problem. Investigators have looked into whether patients who got sick had taken some over-the-counter medicine or folk remedy that actually made things worse.
Such a problem has sometimes occurs in children recovering from flu who are given aspirin – a severe illness called Reyes syndrome, which causes vomiting, lethargy and even seizures. But theres no evidence of something like that in Mexico, Dowell said.
- Altitude or air pollution: Mexico Citys altitude and its infamous air pollution have raised speculation that those factors may have made people more susceptible to the virus. But severe cases are being reported over much of Mexico, including coastal communities and places with cleaner air, making that theory unlikely.
Studies: Drug Shows Guarantee Against Hepatitis C
Still, telaprevir and similar drugs that other companies are testing offer hope of a major advance against the disease, which afflicts about 3.2 million Americans and 180 million people worldwide. It is caused by a bloodborne virus that can lead to liver scarring or liver cancer.
Treatment is aimed at helping the immune system eliminate the virus. Current therapy combines the drugs peginterferon and ribavirin, but less than half on it are cured. Telaprevir and similar drugs under development are a potential game-changer because they specifically attack the hepatitis C virus.
In the two studies, roughly two-thirds given telaprevir with standard therapy for six months showed no signs of the virus after six months, which doctors considered being cured of the disease. Thats compared to 40 to 50 percent on standard treatment alone.
“We can now sit down with our patients and tell them that 2 of 3 patients can be cured with a 24-week course of therapy,” said Dr. John McHutchison, a Duke University doctor who led one study and has consulted for Vertex, based in Cambridge, Mass.
Telaprevir is in late-stage testing and is not available commercially; the company plans to seek government approval next year.
Results were published in Thursdays New England Journal of Medicine.
Hepatitis C is a huge and growing problem because for years there was no way to screen the blood supply for the virus. Infection often doesnt produce symptoms for many years, so many of these cases are just now being recognized even though they may stem from transfusions a decade or more ago.
The virus is mainly spread through contact with the blood of an infected person. It can be contracted by sharing dirty drug needles, getting pricked with a hospital needle with infected blood or being born to an infected mother.
About a quarter of people exposed to hepatitis C clear it out of their bodies without treatment. But the rest develop a lifelong infection that attacks their livers. There is no vaccine against hepatitis C.
In one study of 250 people with chronic hepatitis C in the United States, 61 percent who took telaprevir with standard therapy for six months cleared the virus, compared with 41 percent on standard therapy alone. Among those who took the drug and standard therapy for a year, 67 percent had no signs of infection.
However, twice as many on telaprevir stopped treatment because of side effects.
In another study of 334 people in Europe, 69 percent on telaprevir and standard therapy for six months had undetectable virus levels compared with 46 percent on standard treatment alone.
Testing of even shorter treatment times did not show benefit in either study.
“Telaprevir appears to be a material advance in the therapy of hepatitis C, beginning a new era of treatment,” Dr. Jay H. Hoofnagle of the National Institute of Diabetes and Digestive and Kidney Diseases wrote in an accompanying editorial.
Other doctors were more cautious.
“The new drug does show promise. However, its side effects remain a concern,” said Dr. James Ou, a hepatitis expert at the University of Southern Californias Keck School of Medicine.
Other companies developing similar drugs include Idenix Pharmaceuticals, Schering-Plough Corp. and InterMune Inc.
Us Wants Ingredient In Swine Flu Vaccine By May
Even if all goes well, it still will take a few months before any shots are available for the first required safety testing, in volunteers.
“Were working together at 100 miles an hour to get material that will be useful,” Dr. Jesse Goodman, who oversees the Food and Drug Administrations swine flu work, told The Associated Press.
Using samples of the new swine flu, taken from people who fell ill in Mexico and the U.S., scientists are engineering a strain that could trigger the immune system without causing illness.
“Were about a third of the way” to that goal, Dr. Ruben Donis of the Centers for Disease Control and Prevention said in an interview Tuesday.
The hope is to have that ingredient – called a “reference strain” in vaccine jargon – to manufacturers around the second week of May, so that they can begin their own laborious production work, Donis said.
But, “this is biology, not mathematics,” he cautioned.
To further speed the vaccine hunt, the CDC has shipped a raw sample of the new virus to one manufacturer – Gaithersburg, Md.-based MedImmune LLC, which sells the only flu vaccine given via a nasal spray instead of a shot. MedImmune thus uses a slightly different approach to creating influenza strains suitable for that spray, Donis explained.
Health authorities are struggling to rein in the swine flu epidemic that has sparked a global crisis since discovery of the never-before-seen strain just last week – and the world learned that travelers to Mexico, where dozens may have died, were carrying the bug home.
Standard anti-flu drugs can treat the illness. But the world has no vaccine that prevents this new strain, a mix of pig, human and bird viruses that people presumably have little natural immunity to. And if the virus ultimately spreads enough to spark a pandemic – which hasnt happened yet and may not – a vaccine would be key to mitigating the disaster.
Vaccine manufacturers are just beginning production for next winters regular influenza vaccine, which protects against three human flu strains. Monday, the World Health Organization said factories should stay with that course for now – it wont call for mass production of a swine flu vaccine unless the outbreak worsens globally.
Think of flu viruses as wearing coats, changeable proteins on their surface that trigger the immune system to mount an attack. Those proteins give flu strains their main identity: This new swine flu is part of the Type A/H1N1 family – the “H” being a version of the protein hemagglutinin and the “N” is the protein neuraminidase. Matching those H and N components forms the basis of a vaccine.
First researchers had to grow enough virus samples, culled from a handful of patients, to work with. Influenza virus traditionally is grown by injecting it into fertilized chicken eggs, but this novel virus didnt grow easily there. Theres an alternative, growing it in vats of cells instead, but most flu vaccine manufacturers today still rely on eggs.
Next, using a technique called reverse genetics, scientists are selecting genes for the swine flus H and N antigens to create a customized strain and look for signs that it will prompt a good immune response. Then manufacturers would get the strain to start their own production supply, which could take another two months.
“Its worth taking that time at the very beginning to really make sure youve got exactly what you want,” said MedImmune senior director Dr. Kathleen Coelingh. “Weve got to get this right.”
But those initial pilot lots will go straight into human safety tests already being planned, Goodman said. Flu vaccine in general is very safe. But in 1976, thousands claimed side effects from a swine flu vaccine administered after an outbreak at Fort Dix, N.J., that never spread.
For now, manufacturers are studying production options. Sanofi Pasteur, the worlds largest flu vaccine maker, just opened a new U.S. factory but if necessary could keep its older one open as well just for swine flu vaccine production, said spokesman Len Lavenda. It also produces vaccine at a factory in France.
At Novartis AG, spokesman Eric Althoff said the company is studying which of its two technologies for vaccine-making would be better. The Swiss drugmaker can make vaccines both in eggs and in cell culture.
Glaxo, Roche Meet Swine-flu Drug Needs; Vaccine Is Months Away
Glaxo increased output of its flu remedy Relenza during the weekend, the London-based company said. Roche is also making more of its medicine Tamiflu, said Martina Rupp, a spokeswoman for the Basel, Switzerland-based drugmaker.
Swine flus spread in Mexico, the U.S. and Canada is heightening concern that the virus may spark the worlds first influenza pandemic since the 1968-1969 Hong Kong flu, according to the World Health Organization. That outbreak killed an estimated 1 million people worldwide, according to U.K. researchers. Seasonal flu shots typically take three to six months to make, not counting lab time needed to develop a version tailored to specific strains.
“The vaccine wont be available for quite some time, at least four months, and then it wont be in huge numbers,” said Othmar Engelhardt, a virologist at the U.K.s National Institute for Biological Standards and Control, in Potters Bar, England, north of London.
Sanofi-Aventis SAs vaccine unit is “ready to work” with world health authorities if they ask, said Pascal Barollier, a spokesman for the Paris-based drugmaker. Developing a swine-flu vaccine would take about four months, he said.
Baxter International Inc., which makes both seasonal and pandemic vaccines, has requested samples of the swine virus to do laboratory testing and potentially make shots, said Christopher Bona, a spokesman for the Deerfield, Illinois-based company. Baxters Vero-cell technology can produce flu vaccine in about half the time required by traditional egg-based manufacturing, which takes about 24 weeks, Bona said in a telephone interview.
Baxter Expertise
“Baxter has the expertise to develop vaccines against potential pandemic flu viruses,” Bona said. He declined to say how quickly after receipt of the swine virus the company might have a vaccine ready to enter production.
Homeland Security Secretary Janet Napolitano said 25 percent of “courses of treatments” of antiviral drugs were being released from U.S. stockpiles. In all, there are 50 million courses, she said. Among those are Tamiflu and Relenza.
“Tamiflu, made by Gilead and Roche, and Relenza, made by GlaxoSmithKline Plc, will be natural beneficiaries as stockpiles of these medicines should need replacing,” Les Funtleyder, an analyst with Miller Tabak & Co. in New York, said in a note to clients. “Flu vaccine makers Glaxo and Sanofi Aventis SA could also see some upside as we would expect vaccination rates going into the fall would be significantly higher than in years past.”
400 Million Treatments
Roche can produce 400 million treatments of Tamiflu over a 12-month period, said James Smith, the drugmakers medical leader for Tamiflu, in an interview. “Production capacity now basically outstrips demand.”
How much vaccine makers benefit from swine flu may depend on how fast they can get samples of the swine virus from public- health officials and develop an inoculation in their labs.
“We dont think that any of the existing vaccines are effective,” said Richard Besser, the acting head of the U.S. Centers for Disease and Prevention, based in Atlanta. “There are discussions ongoing about whether to make a vaccine and whether that should be undertaken. Its not an easy decision.”
Developing a flu vaccine can take weeks. Then it takes at least six months to make the vaccine in quantity, according to the CDC. Makers generally start work in January each year on the vaccines that will be used in the flu season that begins in October, the CDC said.
Mutating Virus
Fears of a lethal pandemic lie in the nature of flu germs, which mutate readily and can become virulent by exchanging genes with related influenza viruses. While the H5N1 bird flu that has killed more than 250 people hasnt gained genes to spread easily among humans, the Mexican swine flu already may have done so, said Malik Peiris, a microbiologist from the University of Hong Kong.
“The concern is that this virus has the ability to transmit from humans to humans because a number of the cases who got infection have had no direct exposure to swine,” said Peiris, who has studied the virus behind severe acute respiratory syndrome, or SARS, and avian flu. There is no vaccine for the strain, he said.
Flu Similarities
How Who Measures A Pandemic
- Phase 1. There are no viruses circulating in animals that have been reported to cause infections in humans.
– Phase 2. An animal flu virus has caused infections in humans in the past and is considered to be a potential pandemic threat.
– Phase 3. An animal or mixed animal-human virus has caused occasional cases or small clusters of disease, but the virus does not spread easily. The world is currently in phase 3, with H5N1 bird flu viruses sporadically infecting humans and occasionally spreading from human to human.
– Phase 4. The new virus can cause sustained outbreaks and is adapting itself to human spread.
– Phase 5. The virus has spread into at least two countries and is causing even bigger outbreaks.
– Phase 6. More outbreaks in at least two regions of the world; the pandemic is under way.
If the World Health Organization raises its pandemic alert level to 4 or 5, that signals that the swine flu virus is becoming increasingly adept at spreading between humans. That would signal to governments they should ready their pandemic preparedness plans and increase detection systems for potential cases.
With an elevated pandemic alert level, WHO might also issue travel advisories, warning against nonessential travel to regions battling outbreaks, trade restrictions, the cancellation of public events or border closures.
During the SARS outbreak in 2003, WHO travel advisories drastically slashed travel to affected regions, curtailing the outbreak.
Novartis Drug Heralds Era Of New Multiple Sclerosis Therapies
In Seattle this week, the two companies will present results from late-stage trials of two oral drugs. If the products go on to win regulatory clearance, patients for the first time will be able to take pills, rather than shots or transfusions, to slow the muscle-wasting condition. Five more pills and two new infusion therapies may join the now $7.5 billion a year MS market by 2014, according to the National Multiple Sclerosis Society in New York.
Progress against MS is coming on three fronts, said John Richert, a doctor who leads research at the society. The new drugs may reduce the frequent relapses most patients face. Improved detection may allow earlier treatment before symptoms emerge. Stem-cell therapies now being tested may go even further, reversing disability in patients with advanced disease.
“In terms of stopping disease activity, there are more therapies coming onstream than ever before and many of these also appear to be more potent,” Richert said in a telephone interview. “While the whole idea of repairing the nervous system really seemed like science fiction five to six years ago, advances in the last year suggest this may well be within our grasp.”
First described 140 years ago, multiple sclerosis causes the body to attack itself through the immune system. Rogue immune cells travel to the brain and spinal cord and enter the nervous system. There the cells assault and destroy myelin, the fatty substance that surrounds nerve-cell fibers. That interferes with the nerve cells ability to transmit electrical impulses and move muscles.
Taking a Fall
MS generally starts in early adulthood, disrupting peoples coordination and balance and sometimes leading to damaged vision and paralysis. For Rhonda McHenry, a fall in 1994 while chasing her then 9-month-old son, and the resulting nerve pain, led to an MS diagnosis.
McHenry, now 44, was diagnosed with the “relapsing- remitting” form of MS that makes symptoms flare and recede and that 85 percent of patients have initially, according to the MS Society.
In one way, she was fortunate. Around the time of her diagnosis, three new drugs made from proteins called beta interferons were approved to prevent MS relapses.
The new treatments included Avonex, made by Biogen Idec Inc. of Cambridge, Massachusetts; Betaferon, made by Bayer AG of Levrkusen, Germany; and Copaxone, a product from Teva Pharmaceutical Industries Ltd., of Petah Tikva, Israel.
Inhibit Immune Response
These products, along with Rebif, made by Merck KGaA, of Darmstadt, Germany, inhibit the overactive immune response found in MS, reducing damage to nerves and slowing disability, Richert said. Rebif was approved by the U.S. Food and Drug Administration in 2002.
As researchers have learned more about how the immune system attacks nerves, they have been able to design drugs that interfere with that process, Richert said.
Blocks Cell Movement
The newest MS treatment on the market, Biogens Tysabri, blocks the movement of immune cells from the bloodstream into the nervous system.
The experimental Novartis drug FTY720 disrupts the movement of immune cells at an earlier stage than Tysabri, keeping them from leaving lymph nodes and entering the bloodstream, according to Richert.
German Merck is attempting to turn a cancer drug, cladribine, into an MS medicine because it suppresses the immune system, blunting its attack on nerve cells. The product was approved to treat leukemia more than a decade ago.
Novartis, based in Basel, Switzerland, and Merck will release results this week at a Seattle meeting of the American Academy of Neurology, a professional association based in St. Paul, Minnesota. Preliminary findings already released by both companies suggest that the drugs limit relapses.
Side Effects Key
Doctors Urge Baseline Test For Prostate Cancer
“Many men do not need yearly screening,” but each mans risk should be individually assessed, said Dr. Peter Carroll, who led the panel that wrote the American Urological Associations new guidelines. They are being issued Monday at the groups annual meeting in Chicago.
The new stance brings the group more in line with advice from other experts, who say annual screening is leading to unnecessary biopsies and treatment with little proof that it saves lives. Screening involves a physical exam and a blood test for a substance called PSA.
The urology groups new advice says men should be offered a baseline PSA test at age 40, and follow-ups at intervals based on each mans situation. A high PSA at age 40 greatly predicts a risk of prostate cancer, said Carroll, a urologist at the University of California at San Francisco.
Doing a baseline test “makes a lot of sense to me,” said Dr. Eric Klein, prostate cancer chief at the Cleveland Clinic.
Others disagreed. There is no proof that a baseline test will save lives, said Dr. Barnett Kramer, a National Institutes of Health scientist.
“The same issue of harm comes up – overdiagnosis. A baseline PSA, just like regular PSA screening, can lead to the diagnosis of cancers that would not have harmed a man had they not been detected,” Kramer said.
Prostate cancer is the most common non-skin cancer in American men. An estimated 186,000 new cases and 28,660 deaths from it occurred last year.
Cases rose in the late 1980s with the start of testing for prostate-specific antigen, or PSA, a substance the prostate produces when it is inflamed. Despite its name, PSA isnt very specific. It can rise for many reasons besides cancer, such as normal prostate enlargement as men age, use of certain medicines – even things like a hard bike ride or recent sex.
Two big studies last month concluded that annual PSA tests do little to prevent deaths from prostate cancer. But many doctors believe the test may still have value – if researchers can figure out better ways to use it.
New studies at the urology meeting suggest ways. One found that a mans PSA at age 60 can strongly predict whether he ultimately will die of the disease.
Dr. Hans Lilja of Memorial Sloan-Kettering Cancer Center in New York tested stored blood samples from nearly 1,200 Swedish men from the early 1980s and checked cancer registries to see how many later developed or died of prostate cancer.
If PSA was 1 or less at age 60, the risk of dying of prostate cancer by age 85 was very low – less than 1 percent – even if men had the disease for many years. About 90 percent of cancer deaths occurred in men whose PSAs at age 60 were in the top one-fourth of the group.
“The bottom line is if youve got a PSA of less than one in your initial screen, you can wait to get another PSA for five years and not really be at increased risk of missing a cancer,” he said. “If your PSA is between 1 and 2, its also a small risk.”
Crawford is the unpaid chairman of the Prostate Conditions Education Council, an industry-supported group that promotes screening.
Dr. Robert Uzzo, a prostate surgeon at Fox Chase Cancer Center in Philadelphia, said many doctors are already advising longer testing intervals.
“Everybody has to get screened at least at some baseline” to sort out future testing needs, he said. “If the baseline is quite low then I dont insist on yearly screening.”
Dr. Otis Brawley, the American Cancer Societys chief medical officer, believes there is still some value to PSA testing, but added: “I am very concerned that the urology community and the American public may think theres more value in PSA than there actually is.”
Cholesterol Drugs May Protect Prostate, Sex Potency, Study Says
Men taking any of several different statin drugs for their cardiovascular health had a threefold lower chance of being diagnosed with prostate cancer compared with those not taking the drugs, according to a 15-year study of men ages 40 to 79 by the Mayo Clinic of Rochester, Minnesota. Those taking any of the medicines, including Merck & Co.s Zocor and Pfizer Inc.s Lipitor, also had a lower incidence in later years of erectile dysfunction, benign prostate enlargement and urinary problems.
Prostate cancer is the leading malignancy affecting men and the second deadliest, with 186,320 cases and 28,660 deaths in the U.S. in 2008, said the American Cancer Society. The new research may not reflect a true drop in prostate cancer, the authors said, because statins may merely lower the levels of one indicator, prostate specific antigen, rather than cancer itself.
“If you are taking a statin for a heart condition or to lower cholesterol, these studies suggest that statins could have other benefits,” said study author Jennifer St. Sauver, a Mayo Clinic epidemiologist. “Its clear we need more information before men are advised to start taking statins for their urological health.”
The findings, being presented at the American Urological Association meeting in Chicago, came from a long-term observational study of 2,447 men in Olmstead County, Minnesota. Beginning in 1990, the study tracked the varied effects of statin use on mens health as they age, researchers said.
Mixed History
An American Cancer Society official urged caution in interpreting the results, noting that statin cancer studies have a history of mixed results.
“Weve had studies over the course of several years that suggested statins have a protective or preventive effect with respect to certain cancers. Subsequent studies failed to support that observation,” said J. Leonard Lichtenfeld, deputy chief medical officer of the society in an April 24 telephone interview. “Are there other potential explanations for what youre seeing? There may be an association but not causation.”
A previous study of 1 million people observed by the American Cancer Societys CPS-II research found no effect of statins on cancer, he said.
Funding Disclosed
The Mayo Clinic research was funded by the U.S. National Institutes of Health and by the research unit of Merck, St. Sauver said.
One-third of the 2,447 men in the study were taking one of several statins. Of those, 38 men, or 6 percent, were diagnosed with prostate cancer. Men not taking statins were three times more likely to develop prostate cancer, researchers said.
While previous studies have suggested a link between statins and prostate cancer prevention, St. Sauver said the strength of the association found in the study was a surprise. “Its very strong. I must say we were pretty excited,” she said in an April 24 telephone interview.
Preliminary
The findings are preliminary, said senior author Jeffrey Karnes, a Mayo Clinic urologist. He added that more medical trials are needed to determine whether statins prevent prostate cancer.
“In the United States, one in six men will develop prostate cancer,” Karnes said in a statement. “Far more will develop heart disease. I tell my patients to take care of their heart — because whats good for the heart is also good for the prostate.”
The prostate, a chestnut-shaped gland beneath the bladder that makes semen to transport sperm, is enlarged in one in four men ages 40 to 50 and half of men ages 70 to 80.
Statins are known to lower prostate specific antigen, a protein that is tested in the blood to assess the chance of prostate cancer, St. Sauver said. In this study, statin drugs may have simply lowered PSA so the men were “less likely to go for a biopsy and get a diagnosis of prostate cancer,” rather than actually preventing tumors, she added.
Participants in the study group took an array of different statin drugs, St. Sauver said, with 40 percent being given simvistatin, marketed as Zocor by Whitehouse Station, New Jersey-based Merck, and 35 percent taking atorvastatin, marketed as Lipitor by New York-based Pfizer. Others took products such as lovastatin, sold by Merck as Mevacor, and pravastatin, sold by Bristol-Myers Squibb Co. as Pravachol.
Probes And Answers About Swine Flu
Q. What is swine flu?
A. Swine flu is a respiratory illness in pigs caused by a virus. The swine flu virus routinely causes outbreaks in pigs but doesnt usually kill many of them.
Q. Can people get swine flu?
A. Swine flu viruses dont usually infect humans. There have been occasional cases, usually among people whove had direct contact with infected pigs, such as farm workers. “Weve seen swine influenza in humans over the past several years, and in most cases, its come from direct pig contact. This seems to be different,” said Dr. Arnold Monto, a flu expert with the University of Michigan.
Q. Can it spread among humans?
A. There have been cases of the virus spreading from human to human, probably in the same way as seasonal flu, through coughing and sneezing by infected people.
Q. What are the symptoms of swine flu?
A. The symptoms are similar to those of regular flu – fever, cough, fatigue, lack of appetite.
Q. Is the same swine flu virus making people sick in Mexico and the U.S.?
A. The Centers for Disease Control and Prevention said the Mexican virus samples match the U.S. virus. The virus is a mix of human virus, bird virus from North America and pig viruses from North America, Europe and Asia.
Q. Are there drugs to treat swine flu in humans?
A. There are four different drugs approved in the U.S. to treat the flu, but the new virus has shown resistance to the two oldest. The CDC recommends the use of the flu drugs Tamiflu and Relenza.
A. The seasonal flu vaccine used in the U.S. this year wont likely provide protection against the latest swine flu virus. There is a swine flu vaccine for pigs but not for humans.
Q. Should residents of California or Texas do anything special?
A. The CDC recommends routine precautions to prevent the spread of infectious diseases: wash your hands often, cover your nose and mouth when you cough or sneeze, avoid close contact with sick people. If you are sick, stay at home and limit contact with others.
Q. What about traveling to Mexico?
A. The CDC has not warned Americans against traveling to Mexico but advises that they be aware of the illnesses there and take precautions to protect against infections, like washing their hands.
Swine Flu In U.s., Mexico Lung Illness Heighten Pandemic Risk
A new variant of H1N1 swine influenza has sickened at least seven patients in California and Texas, the Centers for Disease Control and Prevention in Atlanta said yesterday. Mexicos Health Minister Jose Cordova canceled classes in the capital today and recommended citizens avoid public places after 20 fatalities from an illness possibly caused by an H1N1 flu virus.
“The infection of humans with a novel influenza-A virus infection of animal origins, as has happened here, is of concern because of the risk, albeit small, that this could represent the appearance of viruses with pandemic potential,” the European Centre for Disease Prevention and Control said in a statement.
Scientists in both countries and Canada are studying the cases to determine whether they pose a larger public health threat. A pandemic can start when a novel influenza type-A virus, to which almost no one has natural immunity, emerges and begins spreading. Experts believe the so-called 1918 Spanish Flu pandemic, which may have killed as many as 50 million people, began when an avian flu virus jumped to people.
Authorities in Mexico asked the Public Health Agency of Canada to help identify whats causing the lung infection that has also spread to five health-care workers, the Ottawa-based agency said in an e-mail yesterday.
Critical Study
Canadas National Microbiology Lab received 51 specimens from Mexico on April 22 and will be testing them for a range of pathogens, the public health agency said. Tests in Mexico found patients were also infected with the H1N1 and type-B influenza strains and the parainfluenza virus, the agency said.
“It will be critical to determine whether or not the strains of H1N1 isolated from patients in Mexico are also swine flu,” Donald Low, an infectious diseases specialist at Torontos Mount Sinai Hospital, told the Canadian Press.
Thirteen fatal cases of severe respiratory illness were reported in Mexico City; four in San Luis Potosi, a city north of the capital; two in the state of Baja California Norte, bordering California; and another in Oaxaca city in the south. Most cases occurred in southern and central Mexico in previously healthy adults aged 25 to 44 years old.
Symptoms include high fever, headache, eye pain, shortness of breath and extreme fatigue with rapid progression of symptoms to severe respiratory distress in about five days, the Canadian agency said. A “high proportion” of cases require mechanical respiration, it said.
Milder Symptoms
In contrast, the four males and three females in San Diego County and Imperial County, California, and in San Antonio diagnosed with swine flu had mild flu-like symptoms. The patients, aged 9 to 54 years, began feeling unwell from March 28 to April 19. All have recovered and only one was hospitalized briefly, according to the CDC.
Preliminary analyses of the virus indicate it contains four different gene components representing both North American swine and avian influenza, human flu and a Eurasian swine flu.
“Its a real mutt,” Walter Dowdle, who in worked in the CDCs virology unit during a major swine flu outbreak in 1976, told the Center for Infectious Disease Research and Policys daily newsletter yesterday. “When you have an evolving RNA mechanism, its hard to be surprised by anything,” said Dowdle, who now works with the Task Force for Child Survival and Development, based in Atlanta.
Human Infections
Swine influenza is a respiratory disease of pigs caused by type-A influenza that regularly causes outbreaks among the animals, according to the CDC. Swine flu doesnt normally infect people, though human infections do occur and cases of human-to- human spread of swine flu viruses have been documented.
In 1976, 13 soldiers in basic training at Fort Dix in New Jersey fell severely ill from swine flu and one died, prompting concern that a pandemic was unfolding. A vaccine developed to prevent the illness was associated with a paralyzing neurologic illness affecting more than 1,000 people.
Infection in pigs is regarded as especially problematic because of the risk of “reassortment” to produce a new virus, the European Centre for Disease Prevention and Control said.
“These mild U.S. cases infected with a novel influenza are not reflecting the emergence of a pandemic strain, but they at least raise the possibility that there has been limited human- to-human transmission,” the health agency said.