Although the 2009 flu pandemic did not cause the high mortality rates as predicated in June, 2009 when the world health organization (WHO) declared the first pandemic in 41 years, the outbreak reminded us that Influenza remains a major infectious disease and public health challenge. This outbreak reinforced the problems of vaccine production capacity and supply in response to a pandemic. For example, no pandemic H1N1 vaccine was available in most developing countries even more than 8 months after the WHO declared the pandemic . Although the current seasonal Influenza and pandemic H1N1 vaccines have proven to be effective in protecting against infection, the average time frame to manufacture an Influenza vaccine is at least 6 months, which is not sufficient to meet the demands of a pandemic in a timely manner. Moreover, safety concerns still exist for people with egg allergies because the viruses for Influenzavaccines are commonly derived from chicken egg-based cultures. Besides vaccination, antiviral treatment is an important strategy in helping to control and prevent an Influenza pandemic. Two types of antivirals, M2 ion channel inhibitors (Amantadine and Rimantadine) and neuraminidase inhibitors (Oseltamivir and Zanamivir), are commercially available in the United States and have been shown to reduce the severity and durations of fluillness symptoms. Both antiviral treatments have side effects including: lightheadedness, anxiety, chills, nausea, vomiting, loss of appetite and trouble breathing. It is important to note that the 2009 pandemic H1N1 virus (pH1N1) is resistant to M2 inhibitors and an NA-inhibitor resistant pH1N1 strain has also emerged in patients. The emergence of an antiviral-resistant 2009 pH1N1 virus highlighted the urgent need to explore novel antiviral strategies for controlling and preventing Influenzainfection.
No one can predict which subtype will cause the next pandemic. The highly pathogenic H5N1 Avian Influenza virus is able to directly infect humans and have caused more than 60% mortality in infected humans since the first case was reported in Hong Kong, China in 1997. Therefore, the highly pathogenic H5N1 Avian Influenza virus has been thought to be the most likely of all candidates to cause the next pandemic. The H9N2 Avian Influenza virus has been considered to be another candidate causing the next pandemic because infections with this subtype of virus in humans have been reported and normally humans do not have immunity against this subtype of virus. Recently, more than 10 human cases infected with triple reassortant H3N2 Swine Influenza virus containing the M gene from the pH1N1 virus were reported in the USA. The common feature is that these viruses do not have the ability of human-to-human transmission. Nevertheless, if these viruses gained this ability, they will be serious threats for public health. Therefore, it is necessary to prepare vaccines and antivirals for the next pandemic.