MARILYNN MARCHIONE AP Medical Writer SAN FRANCISCO (AP) — Researchers delivered a double dose of good news Sunday in the fight against flu: successful tests of what could become the first new flu medicine in a decade, and the strongest evidence yet that such drugs save lives, not just shorten illness. A single intravenous dose of the experimental drug, peramivir, cleared up flu symptoms as well as five days of Tamiflu pills did, a large study in Asia found. An IV treatment is badly needed because many sick people can't swallow pills and because illness hinders the body's ability to absorb oral medicines. Several other studies showed the value of treatment with Tamiflu. In one study of hundreds of people stricken with bird flu around the world, half of those given Tamiflu survived, while nearly 90 percent of those not given flu medicines died. Other research showed Tamiflu improved survival from regular seasonal flu, too. "There has been an accumulation of evidence over time that the antiviral drugs can save lives," and the new studies confirm that hope, said Nancy Cox, flu chief at the U.S. Centers for Disease Control and Prevention. Results were reported Sunday at an American Society for Microbiology conference in California. It is the first big meeting of infectious disease specialists since the new H1N1 swine flu emerged in April. Treatment options are getting huge attention because it will take a month or more for people to get swine flu vaccine and have time to develop immunity from the shot. In the meantime, reports are streaming in that swine flu is causing havoc in children and young adults. "After about a week of schools being back in, we've seen a tremendous rise in cases," Dr. Jonathan McCullers, an infectious diseases specialist at St. Jude Children's Research Hospital in Memphis, Tenn., said at the conference. In recent weeks, at least 12 children and teens in his city have needed intensive care, including five with no previously known health problems. Some required breathing machines and other life support. One died, and another has developed resistance to Tamiflu, he said. Swine flu now accounts for most flu cases in the United States. More than 1 million Americans have been infected and nearly 600 have died from it, the CDC estimates. Treatment with Tamiflu or a similar drug, Relenza, is recommended for anyone hospitalized with flulike symptoms or at high risk of complications. The drugs should be started within two days of first symptoms, and they shorten illness by about a day. With the drugs in limited supply, and worries about resistance developing to them, new medicines are desperately needed. Peramivir (purr-AM-uh-veer) was tested in nearly 1,100 people with seasonal flu last winter in Asia. They were given either Tamiflu pills for five days or a single infusion of 300 or 600 milligrams of peramivir. Symptoms cleared in about 78 hours and 81 hours with lower and higher doses of peramivir, respectively, and in 82 hours with Tamiflu. Adverse drug reactions were less common with peramivir, said study leader Dr. Shigeru Kohno of Nagasaki University in Japan. The fact peramivir is not a pill like Tamiflu or an inhaled drug like Relenza makes it less convenient yet "very promising" and valuable medically, Cox said. "You can get it into the blood, into the lungs, where infection is occurring," she explained. Others were cautious. "I'm very enthusiastic about peramivir for hospitalized patients," but it was compared in a season when many flu cases were at least somewhat resistant to Tamiflu, said Dr. Frederick Hayden, a virus expert at the University of Virginia and a World Health Organization flu consultant. BioCryst Pharmaceuticals Inc., of Birmingham, Ala., is developing peramivir with Japan-based Shionogi & Co. The U.S. government gave a major grant for its development, and officials have been discussing stockpiling the drug as part of flu pandemic preparedness plans. Tamiflu, made by Swiss-based Roche Holding AG, and Relenza, made by British-based GlaxoSmithKline, came on the market in 1999. Most people who get swine flu don't need them, but these drugs can help save the severely ill, studies sponsored by Tamiflu's maker suggest. The first results from a registry of 215 human cases of bird flu around the world show that nearly 90 percent of patients who did not receive Tamiflu or any other antiviral medicine died, compared with only half of those given Tamiflu treatment. "The earlier it starts, the better," said study leader Dr. Stephen Toovey, a Roche consultant and former employee now at Royal Free and University College of Medicine in London. "Even as far out as eight days after symptom onset, there is still benefit." Others looked at Tamiflu for ordinary seasonal flu: — Researchers at six hospitals in Toronto monitored 238 intensive care patients during three recent flu seasons. Seventy percent were found to have flu, and one-fourth died within 15 days of diagnosis. Patients were nearly three times more likely to survive if treated with Tamiflu, even though very few of them got it soon after symptoms appeared, said Dr. Allison McGeer of Mount Sinai Hospital in Toronto. — About half of 760 people with confirmed flu cases at two hospitals in Hong Kong in 2007 and 2008 were started on Tamiflu within two days. Only 4 percent of them died in the hospital versus 6 percent of those not given an antiviral drug, said Dr. Nelson Lee of the Chinese University of Hong Kong.