However, VE against flu B was similar to what was seen in other age groups, while VE against flu A H3N2 viruses in people 65 and older was significantly lower than in other age groups. CDC recognizes the need for developing better flu vaccines in the elderly. Scientists continued to work on better ways to design, conduct and evaluate non-randomized i. CDC has been working with researchers at universities and hospitals since the influenza season to estimate how well influenza vaccine works through observational studies using laboratory-confirmed influenza as the outcome.
These studies currently use laboratory-confirmed medically-attended influenza virus infections as a specific outcome. Similar studies are being done in Australia, Canada and Europe.
In May and September , flu vaccine manufacturers originally projected about million doses would be available for the U.
Recent updates from manufacturers to CDC indicate that more doses of flu vaccine were actually produced, totaling million doses.
Antiviral resistance means that a virus has changed in such a way that antiviral drugs have become less effective in treating or preventing illnesses caused by the virus. Samples of viruses collected from around the United States and the world are studied to determine if they are developing resistance to any of the antiviral medications currently recommended to treat influenza.
CDC routinely collects viruses through a domestic and global surveillance system to monitor for changes in influenza viruses. CDC also works with the state public health departments and World Health Organization to collect additional information on antiviral resistance in the United States and worldwide. The information assists CDC in making informed recommendations for treatment and prevention of influenza in the United States. To receive weekly email updates about Seasonal Flu, enter your email address:.
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Facebook Twitter LinkedIn Syndicate. However, variant influenza virus infections also can cause serious illness, resulting in hospitalization and death. Seasonal flu vaccines are not formulated to protect against variant influenza viruses, but the same flu antiviral drugs used to treat seasonal flu can be used to treat variant influenza virus infection in children and adults.
In , these infections became nationally notifiable. Since that time, a total of variant influenza virus infections of different influenza A virus subtypes have been identified in the United States and reported to CDC ranging from a high of variant influenza virus infections during the flu season to a low of one during the and seasons The infections reported during the seasons included H3N2v, four H1N2v, and two H1N1v viruses detected during the influenza season.
Following that season, CDC implemented significant education and outreach efforts to raise awareness about the public health concerns related to exposure to pigs. Since then, identification of variant influenza virus infections has been less common, particularly for those associated with agricultural events. Influenza viruses can spread from pigs to people and from people to pigs.
Infected pigs can cough or sneeze and droplets with influenza virus in them can spread through the air. If these droplets land in your nose or mouth, or are inhaled, you can be infected. Pigs can be infected by avian influenza and human influenza viruses as well as swine influenza viruses. When influenza viruses from different species infect pigs, the viruses can reassort i. This is thought to have happened in when a new H1N1 virus with genes of avian, swine and human origin emerged to cause a flu pandemic.
CDC has guidance for people who work or interact with pigs and for people attending fairs where pigs might be present, including additional precautions for people who are at increased risk of serious flu complications. In general, the risk to the public from these infections is considered low, but each case of human infection with a variant influenza virus should be fully investigated to be sure that such viruses are not spreading in an efficient and ongoing way in humans, and limit further exposure of humans to infected animals if infected animals are identified.
Earlier this month, the U. While the virus is not, at this time, transmissible between humans, researchers believe that just a few genetic mutations could change that. Network scientist Alessandro Vespignani, the Sternberg Family Distinguished University Professor of physics, computer science, and health sciences, is mapping the disease's progression in his lab. We asked him to discuss the pandemic potential of the virus and explain how this strain differs from those in the past.
How is H7N9 different from other bird flu viruses we've seen in the past? The H7N9 is a novel reassortant influenza A virus , which very likely originated in birds.
However, the transmission of H7 viruses to mammals has seldom been reported, and human infections with N9 subtype viruses had not been documented anywhere in the world before this outbreak. In addition, most of the observed infections are associated with severe symptoms and a high mortality rate. As of today there have been human cases suggesting that the virus appears to be more infectious to people than most of the other avian influenza viruses we know.
For instance, in China the feared H5N1 is at the origin of less than 50 cases in one decade. Indeed, it appears that the H7N9 virus shows several mutations that make it more adapted to mammals, and thus humans.
What would it take for H7N9 to become a pandemic threat and how concerned are officials about it reaching that point in the near future? So far the virus does not have sustained human-to-human transmission. This means that although there have been small family clusters likely triggered by the prolonged exposure to the infectious individual, the virus cannot spread easily in the general population.
At the moment it is an infection that people catch from animals, however the circulation among humans may favor further genetic adaptation increasing the transmission potential of the virus. Generally these changes are associated with mild and asymptomatic cases that signal an increased adaptation of the virus to the human host.
For this reason, the identification of one asymptomatic case and a few relatively mild cases have raised concerns about the virus. There is an appreciable risk that a pandemic could start if this virus were to change to spread easily between people. The Centers for Disease Control and Prevention, as well as all national and international agencies, are seriously preparing for that possibility. Based on your modeling projections, what impact do you think the H7N9 strain will have on the global population?
At the moment, the lack of human-to- human transmission makes the spreading pattern of the current outbreak not compatible with any widespread epidemic scenario. It is however possible that isolated cases will be observed in other countries because of travelers from China. If the virus acquires the capability of sustained transmission, the situation would be completely different.
In that case it is very likely that the epidemic could escalate to pandemic dimensions in two to three months, as we observed for the H1N1 in Detailed projections, however, would need specific information on the adapted virus, and the initial pattern of spreading. For this reason it is extremely important to increase and enhance surveillance capabilities not just in China but worldwide.
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