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The severity and transmissibility of pandemic influenza viruses result from a complex interaction of viral, host, and external factors. We have come a long way since 1918, and pandemic preparedness programs have learned from the outbreaks of 1918 and subsequent epidemics. Although unlikely, we can not rule out the possibility that a flu pandemic of similar severity will be repeated in the future. However, the lessons learned from the 1918 influenza pandemic will better prepare us. Credit: Kedzierska, Van de Sandt and Short
This year marks the centennial of the 1918 influenza pandemic, the worst flu epidemic ever recorded. A new study on the human, viral and social factors at the root of its gravity provides valuable lessons that could save lives in future pandemics. Publication in The boundaries of cellular and infectious microbiology, underline the authors that, if the world is better prepared than 100 years ago, new challenges will have an impact on the impact of the next influenza pandemic, including the demographic evolution of the population, antibiotic resistance and climate change.
"We have seen three more influenza pandemics since 1918: the" Asian "flu of 1957, the influenza of" Hong Kong "of 1968 and the" swine "flu of 2009. Although they are less serious than the Pandemic of 1918, they testify to the constant threat posed by the influenza virus Katherine Kedzierska, a professor at Peter Doherty University for Infectious and Immune Diseases (Doherty Institute), Australia.
"Like the 1918 pandemic, any future epidemic will be caused by a complex interplay of viral, host, and social factors," says Dr. Carolien van de Sandt of the Doherty Institute. "Understanding these factors is vital for preparing for an influenza pandemic."
The influenza pandemic of 1918 infected one-third of the world's population and killed 50 million people. However, many people have managed to survive a serious infection and others have shown only mild symptoms.
"We have always wondered why some people can effectively control viral infections while others succumb to the disease," said Kedzierska. To investigate this question and explain why the 1918 epidemic was so virulent, Kedzierska, van de Sandt and Kirsty Short, of the Australian University of Queensland, reviewed a large number of studies on influenza.
An explanation of the severity of the pandemic is the viral strain itself. Some studies show that the 1918 virus could spread to other tissues beyond the airways, resulting in larger lesions. In addition, the virus had mutations that allowed it to be transmitted more easily between humans.
Unlike 1918, when the cause of the flu was unknown, scientists today can assess the pandemic potential of new viruses in animals and once a strain has been transmitted to the family. 39; man. But, as the authors point out, such surveillance efforts are needed around the world – a factor that will become even more important with continued climate change.
Electron microscopy of the influenza virus. Credit: CDC
"Climate change is affecting animal reservoirs of influenza viruses and bird migration patterns, which could spread viruses to new locations and among a greater number of bird species," said van de Sandt.
The authors identify public health as another important factor. In 1918, people suffering from malnutrition and underlying diseases such as tuberculosis were more likely to die from infection. This remains a reality today: climate change could lead to crop losses and malnutrition, while increased resistance to antibiotics could lead to an increased prevalence of bacterial infections. Future pandemics will also face the problem of obesity, which increases the risk of death from influenza.
The demography of the population also plays a role. Strangely, one of the most seriously affected groups in 1918 was usually a resilient group, namely young adults. The researchers believe that older people may have been spared due to previous exposure to other viruses, which gives them greater immunity against the 1918 strains. However, since the elderly may have been spared due to previous exposure to other viruses, this gives them greater immunity against the 1918 strains. seasonal flu usually kills older people, the aging of the population will likely be another challenge for any future pandemic.
"The provision of emergency vaccines in future pandemics should take into account the different age groups, viral factors and hosts," said Kedzierska.
The researchers also indicated that the basic methods used to reduce the transmission of diseases, such as the ban on public gatherings and hand washing, had helped reduce levels of infection and death during the pandemic of 1918, but only when they had been applied early and throughout the duration of the pandemic.
"Until a vaccine offering broad protection is available, governments must inform the public what to expect and how to respond to a pandemic," he said. said van de Sandt. "One of the important lessons of the 1918 influenza pandemic is that a well-prepared public response can save many lives."
If a similar pandemic occurred today, scientists estimate that the death toll could reach 147 million. Although it is impossible to know when and how the next flu pandemic will occur, one thing is certain: future pandemics will not look like the 1918 pandemic, but there are still lessons to be learned.
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More information:
The boundaries of cellular and infectious microbiology, DOI: 10.3389 / fcimb.2018.00343, https://www.frontiersin.org/articles/10.3389/fcimb.2018.00343/full
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