Since its discovery in Wuhan, China in late 2019, the SARS-CoV-2 coronavirus has claimed millions of lives in a shock that has changed the way things work. The researchers note that COVID-19 is the worst pandemic since the Spanish flu, which raged on the planet 100 years ago. Scientists from Duke University recently analyzed the frequency of past outbreaks of diseases such as smallpox, cholera, typhoid and influenza, and studied their distribution. The data obtained showed that every year the likelihood of a pandemic similar to COVID-19 is about 2%, that is, such outbreaks will occur on average twice a century. However, the situation is complicated by human intervention in the habitats of wild animals. Using recent estimates of the rate of increase in the incidence of zoonotic viruses associated with environmental change, the study authors concluded that the annual likelihood of extreme epidemics could increase by up to three times in the coming decades. Moreover, according to the 2020 report of the United Nations Intergovernmental Platform on Biodiversity, it was concluded that there are almost a million viruses that can make the leap from animals to humans.
The worst pandemics in human history to date have been the Plague of Antoine, the Black Death from the 1300s to the 1600s, HIV / AIDS, the Spanish Flu, and the Plague of Justinian. Of these, three were caused by one bacterium, Yersinia pestis, which still exists.
Humanity and pandemics
Over the past 30 years, infectious disease outbreaks have occurred with alarming frequency. For example, the World Health Organization (WHO) lists the influenza pandemic and other high-risk viral diseases such as Ebola and Dengue fever among the top 10 public health threats.
The rate of transmission of viruses from animals to humans is increasing, and the US Centers for Disease Control and Prevention estimates that 75% of new infectious diseases in humans originate from animals, the researchers note.
These zoonotic infections can have a profound impact on a person's life. The overall mortality rate from infection is about 10% in severe acute respiratory syndrome (SARS), 40% to 75% in Nipah, and up to 88% in Ebola. While the death rate from Covid-19 infection is lower - probably less than 1% - the overall burden of death is significantly higher, as it affects more than 160 million people.
As countries grapple with the worst global pandemic in a century, it's hard to think about preparing for the next. But if this is not done, the consequences can be disastrous.
Given the fact that the SARS-CoV-2 coronavirus most likely originated naturally (that is, crossed the interspecies barrier), researchers are seriously concerned about the possibility of other epidemics. Today, scientists are attaching increasing importance to the evolutionary theory of viruses, which suggests that animal viruses are gradually becoming dangerous human viruses due to the increased zoonotic spread.
It should also be remembered that an “intermediate” animal, such as a pangolin or a camel, may be required to mutate the virus, but humans themselves may be the final host that allows the variant to fully adapt to the human body.
Increased human contact with wildlife can lead to outbreaks of dangerous viral infections, as viruses jump over species in the process of random mutations that allow them to successfully infect their hosts.
Viral evolutionary theory is evolving in real time with the rapid development of COVID-19 variants. In fact, an international team of scientists has suggested that undetected human-to-human transmission of the virus after jumping from animal to human is the likely source of SARS-CoV-2, the researchers write in an article for The Conversation.
When new outbreaks of zoonotic viral diseases such as Ebola first caught the world's attention in the 1970s, studies of the extent of disease transmission relied on antibody tests, blood tests to identify people who were already infected. Antibody surveillance, also called serology, tests blood samples from target populations to determine how many people have been infected. Serologic testing can help determine if diseases such as Ebola are circulating undetected.
It turns out that it was: antibodies to Ebola were found in more than 5% of people tested in Liberia in 1982, decades before the 2014 West African epidemic. These results support the theory of viral evolution: it takes time - sometimes a long time - to make an animal virus dangerous and transmissible between humans.
New epidemics will emerge more frequently. The reason is rapid climate change and human interference with wildlife habitats.
The diseases we get, like COVID, come from wildlife - and so the more we invade and infiltrate wildlife habitats, the more complex they are and the more likely these emerging events are to occur, '' David Heyman told Newshub. from Massey University School of Veterinary Science.
When to expect the next pandemic?
A paper published in late August in the scientific journal PNAS reported that the most recent pandemics comparable to COVID-19 were the 1957-58 Asian flu pandemic and the 1968-69 Hong Kong flu pandemic, which killed up to 4 million people.
While the death rate from COVID-19 remains a matter of controversy, it is likely to be more deadly than both of these influenza viruses, each slightly more deadly than regular influenza, not to mention the unknown long-term consequences of conditions such as long-term COVID., - write the authors of the scientific work.
Researchers believe that a new pandemic could begin at any time, for example, immediately after COVID-19.
Observational data on epidemic intensity, defined as the number of deaths divided by the world population and the duration of the epidemic, and the incidence of infectious disease outbreaks, are needed to test theory and models and assess public health risk by quantifying the likelihood of extreme pandemics such as COVID -19.
Using recent estimates of the rate of increase in the incidence of zoonotic reservoirs associated with environmental change, the authors of the work concluded that the annual probability of occurrence of extreme epidemics could increase by up to three times in the coming decades. So you and I clearly should not relax, believing that COVID-19 is the only pandemic in our century. As you can see, the results of scientific research prove the opposite.