Some infectious diseases not only take lives but also cause excruciating suffering. Throughout human history, seven horrifying infectious diseases have been recorded, claiming countless lives, and to this day, they evoke fear in many.
Most Deadly Infectious Diseases in the World
Number 7: Tuberculosis
Tuberculosis has caused more deaths than any other infectious disease in history; over one billion people have died in the past 200 years. The origin of the disease is unclear, but it can also infect some other species, including livestock.
Tuberculosis was once a terror to the world, claiming over one billion lives in 200 years. (Image: Freepik).
Today, about one-third of the world’s population is believed to be infected with tuberculosis in its dormant form. This is a state where the bacteria are present in the body but are controlled by the immune system. In this state, patients are asymptomatic and cannot transmit the disease to others.
The bacteria can reactivate in some individuals, causing symptoms such as fever, sweating, weight loss, fatigue, coughing, and coughing up blood.
Tuberculosis occurs in every country. Patients with weakened immune systems due to chemotherapy, HIV, or other underlying conditions are at higher risk of developing tuberculosis.
In 2015, there were an additional 10.4 million new tuberculosis cases and 1.8 million deaths worldwide, primarily in developing countries. The incidence and mortality rates of tuberculosis have decreased globally since the 1900s.
The emergence of antibiotics has allowed humanity to combat this disease. Without antibiotics, 70% of people infected with active tuberculosis would die. However, tuberculosis treatment is often complicated, involving four oral medications for two months, followed by two additional oral medications for the next four months. These drugs all have side effects, and improper use can lead to drug-resistant tuberculosis.
In recent years, drug-resistant tuberculosis has been reported worldwide, most commonly in Russia, China, and India. Treating drug-resistant tuberculosis is much more complex, time-consuming, prone to failure, and often involves more toxic medications.
Number 6: Cholera
Cholera is an acute, highly contagious diarrheal disease caused by the bacterium Vibrio cholerae, characterized by rapid transmission, sudden onset, and high mortality rates. The main clinical symptoms are severe diarrhea and vomiting. The incubation period is typically between 1 to 3 days. Without timely treatment, patients can die from diarrhea and dehydration within hours.
Image: Vibrio cholerae
Cholera primarily occurs when bacteria from contaminated wastewater enter the human body, making water sources and food sanitation the main causes of the disease. The feces of cholera patients contain Vibrio cholerae bacteria, which can contaminate the environment and infect others.
According to estimates by related researchers, there are approximately 1.3 million to 4 million cholera cases and 21,000 to 143,000 deaths globally each year. Cholera typically occurs in areas with poor sanitation, poverty, war, and overcrowding.
Number 5: Ebola
Ebola hemorrhagic fever is a highly infectious disease caused by the Ebola virus, first discovered in Africa in the 1970s. Ebola virus disease is the deadliest type of hemorrhagic fever, with patients ultimately succumbing to widespread hemorrhaging.
Infected individuals typically experience a sudden high fever, sore throat, headache, muscle pain, and weakness, followed by diarrhea and vomiting. Usually within two weeks after the onset of the disease, the body experiences hemorrhaging due to the virus, and patients may die within 24 hours, often in horrific conditions.
Image: Healthcare workers handling the body of an Ebola patient.
The incubation period of the Ebola virus in humans is usually between 2 to 21 days, with transmission primarily occurring through bodily fluids, including blood, vomit, and feces, the latter being the most infectious. Importantly, there is currently no effective treatment for Ebola, and the mortality rate is extremely high, leading the World Health Organization (WHO) to classify it as one of the most dangerous viruses to humans.
Number 4: Spanish Flu
Many people think of the flu as a mild illness, but the Spanish Flu was not just an ordinary flu; it directly caused the deaths of approximately 100 million people.
Patients with Spanish Flu exhibit symptoms such as high fever, headaches, loss of appetite, cyanosis, muscle aches, and coughing up blood. The mortality rate among young people aged 20 to 35 was notably high; many patients showed no symptoms in the morning and fell ill by noon, dying that very night.
The Spanish Flu directly caused the deaths of approximately 100 million people.
During World War I, the Spanish Flu ravaged the world, killing 25-40 million people within six months; it was even a factor in the early conclusion of World War I.
However, the Spanish Flu mysteriously disappeared after 18 months of devastation, and the strains responsible have yet to be fully identified to this day.
Number 3: Plague – The Black Death
The plague, also known as The Black Death, is typically endemic to rodent species. The transmission of the plague occurs through bites from rodent species and fleas, which transfer the pathogen from rats to humans, leading to person-to-person transmission.
This is a highly contagious disease that can also spread through respiratory droplets. If left untreated, the mortality rate can be as high as 50-70%. Subsequent studies discovered that the pathogen of the plague is a type of bacterium known as Yersinia pestis.
Image: The body of a plague patient being taken to a quarantine area.
Throughout human history, there have been many devastating plague pandemics that dramatically reduced the global population and paralyzed society. In the latter half of the 20th century, humanity finally controlled the plague, and it is now very rare.
Number 2: Malaria
Malaria is an infectious disease caused by parasites transmitted by the bite of female Anopheles mosquitoes, infecting those bitten.
Malaria is one of the biggest killers in human history.
The main symptoms of malaria include sudden high fever and chills, accompanied by fatigue and headaches. Malaria is one of the biggest killers in human history, seemingly coexisting with human development.
Approximately 5,000 years ago, malaria gradually spread from Africa to the world, culminating in a global outbreak in the early 20th century. In the past 100 years, malaria has caused approximately 300 million deaths worldwide, and over 1 million people still suffer and die from malaria today.
Number 1: Smallpox
Smallpox is a severe infectious disease that poses significant harm to humans. Once infected, symptoms of systemic toxicity appear, such as sudden high fever, chills, headache, extreme fatigue, and body aches. As the disease progresses to a certain extent, patients will develop rashes that resemble papules, pustules, and blisters.
In the past, due to the lack of effective treatment methods, the mortality rate from smallpox was very high, and survivors often left scars on their faces.
Image: Smallpox Virus
The smallpox virus has a strong ability to reproduce and infect, and can survive for several months after the patient has died; even a piece of scab fallen from an infected person can transmit the disease. It is estimated that around 500 million people worldwide have died from smallpox.
With the advent of the vaccine, humanity has finally eradicated smallpox. In 1980, the World Health Organization (WHO) announced that smallpox had been completely eliminated. To date, only a few strains of the virus are preserved in advanced laboratories.
Although there will still be new infectious diseases to challenge humanity, at this moment, it is COVID-19. However, thanks to advancements in medicine, we have the ability to overcome infectious diseases and have made significant achievements in controlling and preventing them.
