Influenza prevention

Influenza prevention involves taking steps that one can use to decrease their chances of contracting flu viruses, such as the Pandemic H1N1/09 virus, responsible for the 2009 flu pandemic. Influenza prevention involves taking steps that one can use to decrease their chances of contracting flu viruses, such as the Pandemic H1N1/09 virus, responsible for the 2009 flu pandemic. People who contract influenza are most infective between the second and third days after infection, and infectivity lasts for around ten days. Children are much more infectious than adults and shed virus from just before they develop symptoms until two weeks after infection. The transmission of influenza can be modeled mathematically, which helps predict how the virus will spread in a population. Influenza can be spread in three main ways: The relative importance of these three modes of transmission is unclear, and they may all contribute to the spread of the virus. In the airborne route, the droplets that are small enough for people to inhale are 0.5 to 5 µm in diameter and inhaling just one droplet might be enough to cause an infection. Although a single sneeze releases up to 40,000 droplets, most of these droplets are quite large and will quickly settle out of the air. How long influenza survives in airborne droplets seems to be influenced by the levels of humidity and UV radiation: with low humidity and a lack of sunlight in winter probably aiding its survival. As the influenza virus can persist outside of the body, it can also be transmitted by contaminated surfaces such as banknotes, doorknobs, light switches and other household items. The length of time the virus will persist on a surface varies, with the virus surviving for one to two days on hard, non-porous surfaces such as plastic or metal, for about fifteen minutes from dry paper tissues, and only five minutes on skin. However, if the virus is present in mucus, this can protect it for longer periods. Avian influenza viruses can survive indefinitely when frozen. They are inactivated by heating to 56 °C (133 °F) for a minimum of 60 minutes, as well as by acids (at pH <2). According to the World Health Organization (WHO), the 'main route of transmission of the pandemic influenza virus seems to be similar to seasonal influenza, via droplets that are expelled by speaking, sneezing or coughing.' One of WHO's recommendations is to 'keep your distance from people who show symptoms of influenza-like illness, such as coughing and sneezing (trying to maintain a distance of about 1 metre if possible).' Other WHO recommendations are listed below. The American Center for Disease Control and Prevention (CDC) agrees that the 'spread of novel H1N1 virus is thought to occur in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing or sneezing by people with influenza.' The CDC also says that a person may become infected if he or she touches something with flu viruses on it 'and then touches his or her eyes, nose, or mouth.' Reasonably effective ways to reduce the transmission of influenza include good personal health and hygiene habits such as: not touching your eyes, nose or mouth; frequent hand washing (with soap and water, or with alcohol-based hand rubs); covering coughs and sneezes; avoiding close contact with sick people; and staying home yourself if you are sick. Avoiding spitting is also recommended. Although face masks might help prevent transmission when caring for the sick, there is mixed evidence on beneficial effects in the community. Smoking raises the risk of contracting influenza, as well as producing more severe disease symptoms. Thus, according to the laws of mathematical modelling of infectious diseases, smokers raise the exponential growth rates of influenza epidemics and may indirectly be responsible for a large percentage of influenza cases.