Deadliest Diseases in History
The Black Death: Bubonic Plague
The Black Death ravaged most of Europe and the Mediterranean from 1346 until 1353. Over 50 million people died, more than 60% of Europe's entire population at the time.
Many historians believe it started in the Steppes of Central Asia, a vast area of grassland that even today still supports one of the world's biggest plague reservoirs - an area where rodents live in great numbers and density (also called a plague focus).
Plague is mainly spread through the bite of a flea infected with the plague-causing bacterium, Yersinia pestis. Fleas typically live on small animals such as rats, gerbils, marmots and squirrels and periodically, explosive outbreaks of plague occur among these susceptible hosts. Huge numbers of animals succumb to infection and die. Hungry fleas turn to humans and within three to five days of a bite, fever, headache, chills, and weakness develop. Lymph nodes closest to the bite site swell to form a painful bubo in the variant of plague known as bubonic plague. Infection may spread throughout the blood stream and affect respiration in the lungs. Without prompt antibiotic treatment, 80% of infected people die within five days.
The Speckled Monster: Smallpox
The origins of smallpox have been lost in prehistory but research suggests it first appeared around 10,000 BC. Telltale pockmarks adorn the the mummified remains of the great Egyptian Pharaoh Ramses V (dated at 1156 BC) and the disease is described in ancient Sanskrit texts.
Smallpox is caused by the variola virus. Humans are the only natural hosts of smallpox and transmission depends upon direct contact with an infected person or infected bodily fluids, contaminated bedding or clothing. Airborne transmission is rare, although is more likely in enclosed settings such as buildings, buses, and trains.
An incubation period of up to 17 days (average 12 to 14 days) follows exposure to the virus and people are not contagious at this time. Initial symptoms are generally flu-like before small spots start to develop inside the mouth and on the tongue. Within 24 hours a rash starts on the face and quickly spreads before evolving into raised volcano-like pustules filled with a thick, opaque fluid. These pustules may take up to two weeks to scab over, leaving marks on the skin that eventually become pitted scars.
Ebola
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.
Even though the World Health Organization (WHO) declared the end of Ebola outbreak in Liberia on the 9th of June, 2016, there is always a risk of Ebola in countries with very weak health systems and where the virus is prevalent in wild animals. Since 2018, the eastern Democratic Republic of Congo (DRC) has been experiencing an outbreak, with efforts to contain it hampered by conflict and violence in the area. On 1st June, 2020, a new Ebola outbreak was detected in northwest DRC. As of 31 May 2020, 3195 cases of Ebola have been reported, including 72 deaths. The country also battling COVID-19 and the world's largest measles outbreak, with 369 520 cases of measles and 6779 deaths reported.
In December 2019, Ervebo (Ebola Zaire Vaccine, live) was approved for adults over the age of 18. Ervebo is administered as a single dose, intramuscularly. It is not known how long Ervebo protects against Ebola for.
Polio: The Most Dreaded Childhood Disease Of The 1940-50s
Polio is a crippling infectious disease that is often fatal. Children under the age of five are especially susceptible. Although periodic epidemics occurred during the late 19th century, it was the spike in prevalence that occurred in the 1940s and early 1950s that triggered the start of the worldwide campaign of polio vaccination.
Polio is caused by the very contagious and resilient poliovirus and spreads from person-to-person, most commonly though contact with infected feces. Feces can remain infectious for several weeks, as can food, water, or objects contaminated by feces. Approximately 72% of people who catch polio show no symptoms. Twenty-five percent develop flu-like symptoms (for example, sore throat, fever, tiredness, headache, nausea, abdominal pain) within a week or two after infection. A small proportion of these people will go on to develop more severe symptoms such as paresthesia (burning or prickling limb pain), meningitis (infection of brain and spinal cord), limb weakness, and paralysis that may lead to permanent disability and death if the respiratory muscles are affected.
Rabies
This image of the rabies virus, taken through an electron microscope, shows particles of the virus itself, as well as the round structures called Negri bodies, which contain viral proteins.(Image credit: CDC/ Dr. Fred Murphy)
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
The human immunodeficiency virus (HIV, in green), infecting a cell. Image taken with an electron scanning microscope.(Image credit: Cynthia Goldsmith, Centers for Disease Control and Prevention)
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.
0 Comments