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One hundred years ago, almost every day, the flu season seemed to be over without further incident. Most of those who became ill in the spring were quickly recovering and mortality rates were not higher than usual. World news was dominated by news of the Great War, not the flu.
In the fall, however, everything has changed. The virus, which was not exceptional, has re-emerged as an extremely virulent strain, tearing populations in North America and Europe and often killing its victims in a matter of hours or days. In the space of four months, the Spanish flu, as it was called, had spread all over the world, reaching even the most isolated communities. In the following spring, about 50 to 100 million people, or 5% of the world's population, died when the pandemic died out.
A century later, the 1918 pandemic seems to be a horror story as distant as that of smallpox, bubonic plague, and other deadly diseases that we have totally or largely eradicated. However, the flu has never left: it continues to make between 250,000 and 500,000 victims each year. Each year, a slightly different strain of seasonal flu is transmitted, while pandemics can be caused by an assortment of influenza viruses in host hosts. In addition to 1918, pandemics occurred during the last century in 1957, 1968, 1977 and 2009.
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Given the propensity of the virus for mutation and its constant presence in nature (it occurs naturally in wild waterfowl), experts agree that it only takes a few moments before Appearance of a strain as contagious and deadly as the Spanish flu – and perhaps even worse.
"Influenza pandemics are like earthquakes, hurricanes and tsunamis: they happen and some are worse than others," said Michael Osterholm, director of the Center for Infectious Disease Research and Policy. 39, University of Minnesota. "The idea that we would not have another event similar to that of 1918 is stupid."
But when that happens, he continues, it's impossible to predict, "All we know, it could start as soon as we speak." It's also impossible to predict how things will unfold when a strain resembling the Spanish flu will reappear – but we can make informed assumptions.
First, the impact of the virus would depend on how quickly we detect it, says Robert Webster of the Department of Infectious Diseases at St Jude Children's Research Hospital. There are systems in place for this: the World Health Organization influenza surveillance team continuously monitors the virus's progress in six key laboratories around the world, and a complementary set of labs focused on agriculture does the same for poultry and pork samples.
"Our surveillance is probably as efficient as possible, but we can not investigate all the birds and hogs in the world. It's just not possible, "says Webster. "We should have the chance to contain it."
As history shows, deaths are unlikely to be evenly distributed among
The reality, he continues, is that the virus would almost certainly disappear. Once that happens, it will spread all over the world, probably in a few weeks, given the current level of mobility. "Influenza is one of the viruses that, once infected by a vulnerable population, really takes off," says Gerardo Chowell, professor of epidemiology and biostatistics at Georgia State University. "Individuals are already spreading it about a day before they have no symptoms."
Since the number of human beings on the planet has more than quadrupled in the last century, the number of infections and deaths would be proportionately higher compared to 1918. If the flu kills 50 million people in 1918, we could expect more than 200 million victims today. "It's a lot of body bags – that we missed very quickly."
As history shows, deaths would probably not be evenly distributed among populations. The Spanish flu has recorded a mortality difference 30 times higher in different countries. In India, for example, the virus killed 8% of the population, while less than 1% died in Denmark. Similarly, during the 2009 H1N1 flu pandemic, the number of deaths in Mexico was 10 times higher than in France.
Experts believe that the disparities have been influenced by a number of factors, including the past exposure of a population to similar influenza strains and the genetic vulnerabilities of some ethnic groups (Maori New Zealand, for example, were seven times more likely to die after contracting the 1918 flu). the world average).
According to Chowell, poverty-related factors such as sanitation, basic health and access to care also play an important role in the influenza virus's influence. "In 2009, in Mexico, many people came to the hospital only after becoming very, very sick, and it was too late," he says. For many of these victims, it was an economic decision: going to the doctor meant being away from work, and therefore earning a salary. "I'm not saying that this applies to all Mexicans, but that it applies exactly to the most vulnerable populations," Chowell said.
Influenza vaccines – which did not even become available until the 1940s – are faster than ever to manufacture, but this process is still taking months
If a pandemic were to hit the United States or other countries without socialized health services, the same socio-economic trends would almost certainly resemble those of the uninsured. To avoid high medical bills, people without health insurance would probably wait as late as possible to get to the hospital – how possibly it would be too late. "We are already seeing this in terms of other infectious diseases and access to care," Chowell said.
Vaccines are the best way to end a pandemic, says Lone Simonsen, an epidemiologist of infectious diseases at Roskilde University in Denmark and George Washington University. But this first requires identifying the virus, creating a vaccine, and then distributing it around the world – a task easier said than done. Influenza vaccines – which were not even available until the 1940s – are faster than ever to manufacture, but this process is still taking months. And even if we succeed in developing such a vaccine, it would simply be impossible to create enough doses for everyone, says Osterholm. "Worldwide, in the first six to nine months, only 1 to 2 percent of the population would have access to a vaccine," he said. Another limitation, he adds, is that current seasonal flu vaccines are, at best, only 60% effective.
Similarly, although we have medicines like Tamiflu to fight the flu, we do not stock supplies to fight a pandemic. "We do not have enough antivirals today, not even for the richest country in the world, the United States," says Chowell. "So what can we expect from India, China or Mexico?"
In addition to this, the medications we have are also less effective than comparative treatments for other diseases, mainly because "the world views seasonal flu as a rather mundane disease," says Webster. "Only when epidemics are severe, as in the case of HIV, does the scientific community pay more attention to the disease."
Given these realities, hospitals would be swamped quickly, says Osterholm, and drugs and vaccines would run out almost immediately. "We have already flooded the US health care system with seasonal flu this year, and this year has not even been particularly severe," he said. "But it shows how our ability to cope with a significant increase in the number of cases is limited."
If pandemic disrupts production and transport of these drugs, we will see people die – Michael Osterholm
As was the case in 1918, as infections and mortality increased, cities around the world would most likely collapse. Businesses and schools close their doors; public transportation would not work; electricity can go out; and the bodies would start piling up in the streets. There will soon be a shortage of food, as well as essential medicines that support millions of people with diabetes, heart disease, immunosuppressors and other life-threatening problems.
"If a pandemic disrupts the production and transport of these drugs, we will see people die quickly," Osterholm said. "The collateral damage of a 1918 pandemic could be dramatic."
Even after the virus has dissipated, the impacts would be lasting. The 1918 virus was "extra horrible", according to Simonsen, as 95% of the people he killed were not very young or very old, as usual for the flu, but otherwise healthy adults at the peak of their professional lives. This effectively eliminated a significant portion of the workforce and had a profound effect on families, leaving countless orphaned children.
Scientists have only learned why this was probably in 2005, when researchers reconstructed the Spanish flu virus from samples from the Brevig mission, an Alaskan village where 72 of the 80 inhabitants were killed by the disease in less than a week. A victim's body had been sufficiently preserved in the permafrost to allow a microbiologist to recover his lungs, which still contained the virus's genes.
When tested on animals using reconstituted viruses, scientists discovered that the 1918 strain was exceptionally well multiplied. This has triggered a natural immune response called a cytokine storm, during which the body excessively packs by removing chemicals to stop the invasion. Cytokines are somewhat toxic themselves – they are responsible for the pain experienced during a flare-up of influenza – and too many of them can overwhelm the organs and cause an overall system failure.
Adults with stronger immune systems than children and the elderly, researchers believe that their stronger reactions to the flu could be fatal. "We finally understood why the virus was so enormously pathogenic," says Webster. "The body is essentially killed."
We do not do much better with cytokine storms than in 1918 – Michael Osterholm
In the decades following the Spanish flu, researchers have developed various immunomodulatory therapies that can help mitigate cytokine storms. But these treatments are hardly perfect and they are not widely available. "Cytokine storms are not doing much better than in 1918," Osterholm said. "Some machines can breathe and circulate blood for you, but overall, the result is still very dark."
This means that, as in 1918, we would likely experience significant loss of lives among young adults and the middle-aged. And because life expectancy is now several decades higher than that of a century ago, their deaths would be even more damaging to the economy and society, said Chowell.
Despite all the bad news, there is a chance of salvation: a universal flu vaccine. Important resources are finally being allocated to this long-standing dream and efforts to develop such a revolutionary vaccine are gaining momentum. But we can only wait and see if it will happen in time to prevent the next pandemic.
"Studies are underway, so I hope that before the appearance of this hypothetical hot virus, we will have a universal vaccine and that we will be well prepared," Webster said. "But for the moment, we are not there."
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