TOP 12 infectious diseases with most victims

Image of showing a plague doctor's mask

Published on 27/03/2020

The most known and feared lethal epidemics devastated humanity with the help of poor hygiene and weakened organism that support epidemics to spread and get more victims. Before basic sanitary methods had become a habit for most people, streets were covered with faeces and squalor, there were people bathing only once or twice in a lifetime. In that condition, pandemics had no restraint. Although we don’t need to live in the Middle Ages to suffer from a destructive epidemic because nowadays boundless travelling and excessive panic mean the utmost threat in case of a pandemic.

12. Leprosy

Number of victims: unknown
Symptoms: skin sores lumps dumps
Caused by: mycobacterium leprae

There is no available data about the exact number of lives demanded by Leprosy, but today there are approximately 180 000 people infected with leprosy, mostly in Asia and Africa. Leprosy can cause damage to the nerves, skin and eyes, but its mortality is surprisingly humble.

Leprosy has been surrounded by many stigmas since the first presence of it in the Medieval Ages. Nowadays, Hanson’s disease is a more common name in medical statements for this condition, in order to avoid excommunication of patients. Leper houses and hospitals were commonplace on the edge of towns, where lepers could be isolated.

Fortunately, the disease doesn’t spread easily in addition to its quite efficient treatment, but a couple of decades ago, it was said to be a destructive and exceptionally contagious infection. The incubation period of Hansen’s disease is extremely long, it can stay unobserved for 5 years, but cases with latent leprosy for 20 years were also found. It’s a common belief that leprosy makes fingers to fall off, but in fact it’s not a direct consequence of having the disease. As the virus attacks the nerves, causing numbness in the fingers, it is quite common to lose digits by cutting or burning them, because it’s too late when people notice it due to the lack of pain.

11. Ebola

Number of victims: 20,000
Symptoms: diarrhoea body aches bleeding
Caused by: ebola virus

Ebola hemorrhagic fever is an infectious viral disease, which was first identified in 1976. It attacks mainly humans and hominids, but its origin is believed to be bats. Its death rate is considerably high, up to 90% of infected people dies due to the disease. Fortunately, Ebola is quite rare because it doesn’t spread by air, water or food. Catching the disease only happen in case of direct contact with an infected person, so those who nurse or bury victims often get it.

The incubation period for Ebola varies from 2 and 21 days. In advanced stadium of Ebola, the virus causes severe bleeding inside the body and drops of blood from nose, eyes and ears are pretty frequent symptoms, just like coughing up or vomiting blood. Ultimately, the virus develops multi-organ failure, and this causes the death of the infected person.

10. Yellow fever

Number of victims: 50,000
Symptoms: headache fever nausea chills loss of appetite yellow skin
Caused by: yellow fever virus

The virus is spread by mosquitos, mainly in Africa, but due to climate change, mosquitos have become common outside of their original habitat. In addition, deforestation has also helped enhance the quantity of mosquitos by reducing the habitat of birds, mosquitos’ their natural enemy. A highly effective vaccination, called 17D was made 60 years ago, and has been used since then.

The onset of symptoms usually occurs within 3-6 days after infection. In 85% of cases, only lightsome inconveniences develop compared to serious cases, when severe pain, recurring fever, yellowness due to liver damage, vomiting blood and bleeding in the eyes, nose and mouth and occasionally delirium and renal failure occur. The severe cases cause death in more than 50% of the incidents, but those who lucky enough to survive the disease, get lifelong immunity.

9. Typhus

Number of victims: 7 million
Symptoms: rash fever headache dry cough chills
Caused by: rickettsia bacteria

Epidemic, Scrub and Murine typhus are the members of the group of infectious diseases called typhus. It’s spread by lice, fleas or mites. The most common and remarkable form of typhus is Epidemic typhus, so most data is based on the consequences and symptoms of this type of typhus.

Symptoms develop in one or two weeks after exposure to the parasites. There is no generally available vaccine yet, so avoiding the infection is vital in the case of typhus. Outbreaks mostly occur in developing countries where hygiene is poor. The disease was commonplace during wars; many historical records mention epidemics that caused rash, fever, delirium and rotting flesh.

As close human contact is favourable for this infection, outbreaks in jails was a problem in England in the XVI. century. A series of infection outbreaks believed to be typhus claimed hundreds of lives in jails and courts and it sometimes spread even to the residents of the city. There were more prisoners killed by gaol fever than execution, and a couple of weeks in an infected prison until court meant sure death.


Number of victims: 36 million
Symptoms: fever weight loss swollen lymph nodes
Caused by: human immunodeficiency virus

HIV/AIDS is quite a modern pandemic, originated from Africa in 1980. Human immunodeficiency virus causes flu-like symptoms in the early stage four weeks after infection, then stays asymptomatic for the incubation period, approximately 10 years. In those years, the virus stultifies the immune system, making it more responsive for common infections which then cause the death of the person. HIV refers to the latent and mostly harmless period, but when a condition, varying in many different symptoms develop in the body due to the weakened immune system, then it’s called AIDS or 3 HIV. Opportunistic infections are commonly tuberculosis and pneumonia, but some types of cancer are also more likely to grow in a vulnerable body. HIV used to be a feared and deadly disease, but if it’s uncovered and treated before stage 3 (AIDS) evolves, life expectancy is quite relieving, in fact an infected person can live a long, normal life. Additionally, HIV infection is relatively easy to discover, a simple blood saliva test provides accurate results, however after AIDS developed, diagnosis becomes quite complicated. HIV is transmitted by certain body fluids from an infected person. It’s commonly known that sharing needles or having sex is a risk factor of getting HIV, but the virus also spreads through pregnancy, breastfeeding, organ transplant or blood transfusion.

7. Cholera

Number of victims: 40 million
Symptoms: diarrhoea dehydration vomiting
Caused by: bacterium Vibrio cholerae

Over the last two centuries 7 outbreaks rampaged and killed millions of people. Cholera in severe cases kills within hours, however, if rapid treatment is available, recovery is expected in over 95% of cases. After the initial presence of the bacterium in the Ganges (India) during the 19th century, it spread into the water through the faeces of an infected person and infects others. It’s easy to get infected, as cholera is a waterborne disease and is present in water and food, especially in areas where the lack of clean water and sanitation is common. Most of the times seafood is at high risk to be contaminated. Annually, there are an estimated 1 billion cholera cases and approximately 30 thousand death. Children are highly threatened by cholera. Providing sanitation and clean water is the key for fighting against cholera in a long term, but until that, ORS (oral rehydration solution) is the treatment. Symptoms usually occur in two to five days of exposure. Extreme diarrhoea leads to dehydration and electrolyte imbalance in a short period of time, which causes the skin to wrinkle and turn blue.

6. Influenza

Number of victims: 50 million
Symptoms: fever sore throat runny nose headache coughing exhaustion
Caused by: influenza virus

The virus is spread through air or by touching contaminated surfaces and our nose, mouth or eyes afterwards. Symptoms usually appear in two days of exposure and last for a week, except coughing, which sometimes stays for an extra week. Infected people spread the virus both before and during symptoms present, and 33% of people having influenza don’t show symptoms at all, but still spread it. Only one in the four types of influenza (A, B, C and D) has not been proven to be dangerous to humans yet, but it has the potential to do so. This form (type D) attacks cattle and pigs. Influenza genus A caused the most epidemics, like Spanish flu, Bird flu, Asian flu and Hong Kong flu. A flu-season is due every winter, in fact, there are two epidemics of flu in a year, one on the norther and one on the southern hemisphere, both of them during winter in the given area. The good thing about influenza is that you can treat it without seeing the GP if you provide yourself enough sleep and water, take paracetamol or ibuprofen to relief pain and lower high temperature.

5. Measles

Number of victims: 200 million
Symptoms: rash fever runny nose cough sneezing
Caused by: measles virus

Measles is a greatly infectious disease, spread by droplets from cough or sneeze, but an infected person only threat others four days before and after rash appeared. According to statistics, every 9 people out of 10 get infected after a measles outbreak. It is known to be children’s disease, but it can infect people of any age. The bad news is specific treatment for the disease does not available, but taking painkillers, drinking enough water and resting help ease the symptoms until the body heals itself. However, preventive vaccine called MMR has been in use for ages and in some countries it’s compulsory to use. Measles still infects 20 million people annually, mainly in Africa and developing countries of Asia. Death occur if the disease cause inflammation in the brain, but fatal illness is only common among children younger than 5 or older than 20.

4. Plague

Number of victims: 240 million
Symptoms: headache fever weakness
Caused by: yersinia pestis bacterium
Fatality: 60 - 70%

Plague is probably the most feared infectious disease. The bacterium lives in rodents and spread by their fleas and can infect humans and mammals. The main pandemic of plague, called Black Death was the cause of the suffer and death of an estimated 50 million people, probably half of them in Europe, between 1347 to 1351. The scary, raven-like mask on doctors are from this era. It was used to protect them, and they put herbs into the long beak, because they thought it would filter the air.

Symptoms occur after 1 to 7 days to exposure. Three main forms of plague are known to exist in human history, which are bubonic, pneumonic and septicaemic.

Justinian’s plague was the first plague pandemic that is proven to be existed, occurred between 542 AD and 546 AD. It caused the death of 100 million people.

Plague still exists, but modern antibiotics seem to fight off the dangerous disease in Europe. In rural areas of western United States infections still occur, and unfortunately Africa and Asia have more cases than you would think.

3. Smallpox

Number of victims: 500 million
Symptoms: fever rash headache vomiting diarrhoea
Caused by: variola virus

Smallpox spreads through contact with infected people, their body fluids or personal objects. It officially has been eradicated since 1980 after its final outbreak in the USA in 1949 but claimed over 500 million victims throughout history. 30% of people who suffered from smallpox died, but the others carried the consequences of the disease in their entire life, like blindness and scars. Smallpox had been around since pre-historic eras. First evidences were found in mummies, more precisely Egyptian Pharaoh Ramses V., which means the disease was present before his death in 1157 B.C. It was noticed that people who had already had smallpox are unlikely to get it again, so they won a lifelong immunity to the disease. Eradication of smallpox begun as early as the 10th century, in China, because they observed that who got in close contact with matter from smallpox scabs showed less serious symptoms than those who got infected naturally. The method was to blow matter from scabs to a healthy person’s nose. This method is named variolation and later became common prevention of smallpox.

2. Tuberculosis

Number of victims: 750 million
Symptoms: sweating fever cough weight loss blood in mucus fatigue
Caused by: mycobacterium tuberculosis

It has been present since ancient times, came about with the domestication of animals. Tuberculosis is a bacterial infection, so it can be cured with the proper antibiotic treatment, although it needed to be taken for 6 months. Tuberculosis spread by droplets from cough or sneeze from an infected person, although there are cases when an infected person doesn’t show any symptoms also doesn’t infect others, it’s called latent tuberculosis. In this case the bacterium lives in the body without making any harm to it, although it can develop into active tuberculosis. Active tuberculosis on the other hand mainly affects the lungs but can have effects in other parts of the body, causing serious complications, even death. Today it is estimated that one in every four people is infected with tuberculosis, but the majority of them are in Africa and Asia, as 95% of death from tuberculosis occur in these areas.

1. Malaria

Number of victims: 1+ billion
Symptoms: fever vomiting headache diarrhoea
Caused by: plasmodium microorganisms

Malaria is spread by female Anopheles mosquitos, that’s why it’s common in the tropical and subtropical regions and associated with poverty and economic difficulties as medical treatment is extremely expensive and loss of labour contribute to decline. Another way to get the disease is by sharing infected needles or blood transfusion, but these are not that common. The only prevention of malaria is insect repellent or prevention tablets besides avoiding highly hit countries by mosquitos. If malaria is diagnosed in time and treatment is appropriate, there is a high chance to recover, however, less lucky victims easily get serious anaemia or cerebral malaria. There are more than 200 million cases worldwide annually resulting in near half a million death. Not surprisingly malaria has claimed the most lives throughout history among all the infectious diseases.

+1. Coronavirus (COVID-19)

Number of victims: 303,612+
Symptoms: fever cough fatigue breathing difficulties
Caused by: coronavirus

There were cases of other types of coronavirus some years ago, these were the SARS and MERS coronavirus, however in the first months of 2020 this virus keeps the whole world in dread. Most of Europe is in quarantine, panicking and hoarding as much products as they can. Media contributes to this, as in every minute there is a new report on the internet, another famous person speaks about their situation and even fake news are worsening the chance to get over this pandemic in peace. The infection came about in Wuhan, China from a bat in theory in December 2019. The disease is spread easily through droplets from cough or on contaminated surfaces, although it does not bear high temperature and disinfectant, so cleaning is going to be vital in the following months. The incubation period is said to be approximately a week, however it’s such a relief that symptomless infected people do not infect others according to a study. As symptoms get worse, serious cases are needed to be treated in hospital, as the disease decreases the amount of oxygen the body can use, so patients need breathing machine until their condition gets better. There are more than 4,541,366 confirmed cases so far and 303,612 death, but unfortunately these are not the ultimate data about this ongoing pandemic.

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