What are the deadliest viruses in history?

In the first two years of the COVID-19 pandemic, the number of direct or indirect coronavirus deaths was about 15 million people worldwide, according to World Health Organization estimates. The United States has seen more deaths in 2020 and 2021 than during the 1918 flu pandemic, said to be the deadliest flu pandemic in recorded history.

The word “lethal” certainly applies to the virus that causes COVID-19. Nevertheless, epidemiologists hesitate to give SARS-CoV-2 the highest possible rating. the deadliest Viruses in human history. For them, the raw death toll caused by a particular virus does not always paint a complete picture of the pathogen’s danger. This is especially true when comparing virus epidemics over time.

Raw mortality rates need to be calculated considering the world’s total population, he says Jennifer Nuzzo, Professor of Epidemiology and Director of the Pandemic Center at the Brown University School of Public Health. “A lot of people are talking about how the death toll from COVID-19 exceeded what we saw in 1918,” she says. “It’s very important to remember that the 1918 population was only a fraction of today’s population.” In that context, the 1918 flu ranks again in terms of expiration.

If you used the metric “fatality” to determine which viruses are the most lethal, rabies would probably come out on top. This is because when symptoms of an infection appear, Rabies is deadly to humans In more than 99 percent of cases. About 59,000 people die from rabies worldwide each year. In developed countries, these deaths are rare (an average of 2 in the US) and do occur, thanks to rabies vaccines for domestic pets and prompt medical intervention after a bite.

But “even if a virus isn’t very deadly, it can still cause huge numbers of deaths and chaos,” Nuzzo said. “Rather, it is important to look at the environment in which the virus is prevalent and our social and human vulnerability to it.”

A virus with a low fatality rate can still kill more people if it is highly contagious and takes a long time to develop severe or overt symptoms. This allows an infected person to infect many others. That is why SARS-CoV-2 caused such a rapid and devastating epidemic around the world. It is easily transmitted through airborne droplets, but does not always or immediately cause severe illness.

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Globalization has also accelerated it. “There’s a big difference between a virus spreading as fast as a human walks and being able to get anywhere in the world in 36 hours on a plane,” Nuzzo said.

In the event of a large epidemic such as an epidemic or pandemic, epidemiologists turn to another indicator called excess mortality. It tells you how many more people died over a period of time than usual during the same period. Nuzzo said the excess deaths may be due to other indirect causes of deaths caused by the virus, such as patients who need critical care but are not served in overcrowded hospitals.

Here’s how some of the most devastating viruses in human history tell different stories about how the death toll will rise.

influenza

The 1918 influenza pandemic still ranks as the deadliest pandemic of the 20th century. It is thought to be caused by the H1N1 virus, which spread worldwide in 1918-1919. An estimated 500 million people (about one-third of the world’s population) are infected, 50 million dead About 675,000 of them were in the United States, according to the Centers for Disease Control and Prevention.

Without advanced testing and tracking, mortality estimates rely heavily on excess mortality calculations. Some suggest the actual number of victims could be closer to 17 million, while others place it at a much higher figure of 100 million. William SchaffnerA professor of preventive medicine and a professor of medicine in the Department of Infectious Diseases at the Vanderbilt University School of Medicine, he cautions against stretching comparisons between historical flu data and modern viral epidemics.

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“We are now identifying infections and even counting deaths much more accurately than we did then,” he says. There were no flu vaccines or antibiotics to treat secondary bacterial infections at the time, which may have contributed to the excess deaths.

Despite the availability of a vaccine, influenza remains one of the deadliest viruses. Mutants of the influenza virus have caused other pandemic his-level events, such as his 2009 outbreak colloquially referred to as the swine flu pandemic. But the virus is also endemic in our society, infecting an estimated 1 billion people worldwide each year, according to the World Health Organization. Of these cases, WHO reported in 2019. 290,000 to 650,000 lead directly or indirectly to death.

Estimate 40.1 million died from AIDS-related diseases Since the beginning of the epidemic, according to the Joint United Nations Program on HIV and AIDS. This represents almost half of the estimated number of people who have been infected with HIV since the epidemic began (an estimated 84.2 million).

The fatality rate of HIV/AIDS has historically been very high.Some estimates say that about 80 percent without treatment. However, many things have changed since the 1980s. There are now ways to manage HIV and reduce the immunodeficiency associated with infection, and most patients are diagnosed earlier after infection.In the United States, HIV-related mortality is dropped to nearly half From 2010 to 2017, according to the CDC.

Excess mortality indicators likely reached much higher numbers by the time authorities announced them. public health emergency is over in early May. The global Omicron wave in late 2021 and early 2022 was one of the largest spikes in COVID-19 cases. Although this variant did not appear to be any more lethal than the previous variants, millions were infected and hundreds of thousands of deaths were inevitable.

In the early days of the pandemic, calculated fatality rates for SARS-Cov-2 varied significantly. As researchers scrambled to devise tests for the virus and mild cases slipped through, many estimates were likely higher than the real numbers. In early 2020, national fatality rate estimates were: 25 percent or more. Since then, the fatality rate has declined and now stands at 4.9%, according to Johns Hopkins University. in the United States, fatality rate is 1.1 percent.

Mortality continued to rise in the 20th century, with an average of 3 out of 10 infected people dying.The disease is caused by the smallpox virus and is presumed deadly over 300 million It was the first disease to be eradicated from 1900 until a global vaccination campaign halted its devastation in 1977.

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But what made it particularly terrifying was its downfall, Schaffner says. “It caused a very characteristic rash, so people could recognize it and fear it, and that was one of the Achilles heels,” he says. The virus was so easy to identify and spread so slowly that vaccination of local populations close to the outbreak controlled the infection quickly. Such an approach, he says, was part of a vaccination strategy to eradicate the epidemic.