Humans have been battling viruses since before our species had even evolved into its modern form. For some viral diseases, vaccines and antiviral drugs have allowed us to keep infections from spreading widely, and have helped sick people recover. For one disease -smallpox -we've been able to eradicate it, ridding the world of new cases.

But we're a long way from winning the fight against viruses. In recent decades, several viruses have jumped from animals to humans and triggered sizable outbreaks, claiming thousands of lives. The viral strain that drove the 2014-2016 Ebola outbreak in West Africa kills up to 90% of the people it infects, making it the most lethal member of the Ebola family.

But there are other viruses out there that are equally deadly, and some that are even deadlier. Some viruses, including the novel coronavirus currently driving outbreaks around the globe, have lower fatality rates, but still pose a serious threat to public health as we don't yet have the means to combat them.

Marburg virus:

Scientists identified Marburg virus in 1967, when small outbreaks occurred among lab workers in Germany who were exposed to infected monkeys imported from Uganda. Marburg virus is similar to Ebola in that both can cause haemorrhagic fever, meaning that infected people develop high fevers and bleeding throughout the body that can lead to shock, organ failure and death. The mortality rate in the first outbreak was 25%, but it was more than 80% in the 1998-2000 outbreak in the Democratic Republic of Congo, as well as in the 2005 outbreak in Angola, according to the World Health Organization (WHO).

Ebola virus:

The first known Ebola outbreaks in humans struck simultaneously in the Republic of the Sudan and the Democratic Republic of Congo in 1976. Ebola is spread through contact with blood or other body fluids, or tissue from infected people or animals. The known strains vary dramatically in their deadliness, Elke Muhlberger, an Ebola virus expert and associate professor of microbiology at Boston University, told Live Science.
One strain, Ebola Reston, doesn't even make people sick. But for the Bundibugyo strain, the fatality rate is up to 50%, and it is up to 71% for the Sudan strain, according to WHO.

Rabies:

Although rabies vaccines for pets, which were introduced in the 1920s, have helped make the disease exceedingly rare in the developed world, this condition remains a serious problem in India and parts of Africa.

"It destroys the brain, it's a really, really bad disease," Muhlberger said. "We have a vaccine against rabies, and we have antibodies that work against rabies, so if someone gets bitten by a rabid animal we can treat this person," she said. However, she said, "if you don't get treatment, there's a 100% possibility you will die."

HIV:

In the modern world, the deadliest virus of all may be HIV. "It is still the one that is the biggest killer," said Dr. Amesh Adalja, an infectious disease physician and spokesman for the Infectious Disease Society of America.
An estimated 32 million people have died from HIV since the disease was first recognized in the early 1980s. "The infectious disease that takes the biggest toll on mankind right now is HIV," Adalja said. Powerful antiviral drugs have made it possible for people to live for years with HIV. But the disease continues to devastate many low- and middle-income countries, where 95% of new HIV infections occur. Nearly 1 in every 25 adults within the WHO African region is HIV-positive, accounting for more than two-thirds of the people living with HIV worldwide.

Regards,
Alex

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