Epidemic events from 2011 to 2017: 95

Chikungunya is a mosquito-borne viral disease that causes fever and severe joint pain. The disease was first recognized in 1952 during an outbreak in southern Tanzania. The disease occurs in Africa and Asia, although imported cases have been recorded in Europe and the Americas. Over 2 million cases have been reported since 2005. There is no cure.

Epidemic events from 2011 to 2017: 308

Cholera is an acute diarrheal infection caused by eating or drinking contaminated food or water. Researchers have estimated that every year, there are 1.3 million to 4 million cases of cholera, and 21 000 to 143,000 deaths worldwide due to the infection. It can be eliminated with access to clean water and sanitation facilities, as well as good hygiene practices. Above, a child suffering from cholera in Taiz, Yemen, in 2017.

Epidemic events from 2011 to 2017: 49

This viral hemorrhagic fever is usually transmitted by ticks, but can also be contracted from animal tissue where the virus has entered the bloodstream during and immediately after slaughter of animals. The disease has a high fatality rate of 10% to 40%, and is difficult to prevent and treat. CCHF is endemic in all of Africa, the Balkans, the Middle East and in Asia. 

Epidemic events from 2011 to 2017: 22

Ebola is a severe illness affecting humans and other primates with an average fatality rate around 50%. The virus is transmitted to people from wild animals, such as fruit bats, bodily fluids of infected people, and from contaminated surfaces and materials such as bedding. Ebola was first discovered in 1976. The 2014–2016 outbreak in West Africa was the largest. A recent outbreak in the Democratic Republic of Congo is believed to be over with the release of the last patient March 3, 2020. 

Hendra virus infection is a rare emerging disease that can be transmitted to humans from horses and is severe and often fatal to both. Symptoms in humans range from mild influenza-like illness to fatal respiratory or neurological disease. The first recorded outbreak of the disease was in the Australia in 1994. The outbreak involved 21 stabled racehorses and two human cases. There is now a vaccine for horses.

Epidemic events from 2011 to 2017: 51 (Influenza A)

Seasonal influenza is an acute respiratory infection caused by influenza viruses which circulate in all parts of the world. There are four types of seasonal influenza viruses, some of which are classified into smaller categories, some are mild, and one type that affects mainly cattle.

Humans can also be infected with avian, swine and other zoonotic influenza viruses. Human infections are primarily acquired through direct contact with infected animals or contaminated environments; these viruses have not acquired the ability of sustained transmission among humans. According to WHO, influenza viruses, with their “vast silent reservoir in aquatic birds, are impossible to eradicate.”

Epidemic events from 2011 to 2017: 23

Lassa virus causes hemorrhagic fever, meaning multiple organ systems in the body are affected. Humans usually become infected through urine or feces of infected rats. The disease is endemic in the rodent population in parts of West Africa. About 80% of people who become infected with Lassa virus have no symptoms, but one in five infections result in severe disease, where the virus affects several organs such as the liver, spleen and kidneys.

Epidemic events from 2011 to 2017: 4

This is a highly virulent disease that causes hemorrhagic fever, with a fatality rate of up to 88%. It was first recognized when two large outbreaks occurred in Germany and in Serbia in 1967, and was associated with laboratory work using African green monkeys imported from Uganda. It has since appeared in parts of Africa. Humans initially are infected by prolonged exposure to mines or caves inhabited by a certain type of bat, then it can be spread human to human.

Epidemic events from 2011 to 2017: 137

Meningitis is an infection that causes inflammation of brain and spinal cord membranes. It can be caused by viral, bacterial, or fungal infections. It is a serious condition that can be life-threatening.

Epidemic events from 2011 to 2017: 57

Middle East Respiratory Syndrome is a viral respiratory disease caused by a coronavirus that was first identified in Saudi Arabia in 2012. Symptoms include fever, cough and shortness of breath, and sometimes pneumonia. About 35% of reported patients with the infection have died. It is believed that it may have originated in bats and was transmitted to camels sometime in the distant past.

Epidemic events from 2011 to 2017: 10

This virus causes a disease with symptoms similar, but less severe, to smallpox. It occurs in countries of Central and West Africa, and is transmitted from animals such as squirrels, rats, mice and certain monkeys to humans. It has a death rate of about 1%-11%.

Epidemic events from 2011 to 2017: 5

Nipah can be transmitted from animals to humans, and also through contaminated food or directly between people. It causes a range of illnesses from asymptomatic infection to acute respiratory illness and fatal encephalitis. Although Nipah virus has caused only a few known outbreaks in Asia, it infects a wide range of animals and causes severe disease and death in people, making it a public health concern.

Epidemic events from 2011 to 2017: 47

Plague is an infectious disease caused by bacteria and transmitted from animals and fleas to humans. In the Middle Ages, the plague spread from Asia to Europe and killed about 60% of the entire world population. In its severest form, it has a case-fatality ratio of 30% to 100% if left untreated. Today it can be treated with antibiotics.

Epidemic events from 2011 to 2017: 14

Rift Valley fever is a virus that primarily affects animals but also can infect humans. It is transmitted by mosquitoes and blood-feeding flies. In humans, the disease ranges from a mild flu-like illness to severe hemorrhagic fever that can be lethal. No human-to-human transmission of RVF has been documented. It was first identified in 1931 in a sheep epidemic on a farm in the Rift Valley of Kenya, and has since appeared in parts of Africa and the Middle East.

Severe Acute Respiratory Syndrome first appeared in 2002 in China and spread worldwide within a few months, then was quickly contained. SARS is a virus transmitted through droplets that enter the air when someone with the disease coughs, sneezes, or talks. No known transmission has occurred since 2004. Fever, dry cough, headache, muscle aches, and difficulty breathing are symptoms.

Epidemic events from 2011 to 2017: 113

Shigella bacteria is only naturally found in humans and gorillas. It typically causes dysentery and is one of the leading bacterial causes of diarrhea worldwide, with an estimated 80 million to 165 million cases, and between 74,000 and 600,000 deaths each year. It is spread by eating or drinking food or water contaminated with the bacteria.

Smallpox was caused by a virus that was declared eradicated in 1980 thanks to vaccination. It had a death rate of about 30%, and survivors were left disfigured by scarring and sometimes blinded. The disease dates back as far as 5,000 years, and is estimated to have killed up to 300 million people in the 20th century.

This disease is caused by a bacterium that appears in a wide variety of wild mammals and birds. Humans become infected mainly through ticks and mosquitoes, by direct contact with infected animals or animal materials, by ingestion of contaminated food or water or inhalation of contaminated dust. Symptoms may include fever, skin ulcers, and enlarged lymph nodes. There are treatments, and the disease is best prevented by using insect repellents and by not touching dead animals. There are about 200 cases a year in the U.S.

Epidemic events from 2011 to 2017: 75

Typhoid fever is a life-threatening illnesses caused by a Salmonella bacterium. Symptoms include a gradual onset of a high fever over several days, accompanied by weakness, abdominal pain, constipation, headaches, and mild vomiting. Humans are the only known carriers. It is most common in parts of Africa, Asia, and South America. This image from 1898 shows American soldiers in quarantined at Camp Wikoff, Montauk, N.Y., after the Spanish American war, where many were recovering from yellow fever, malaria and typhoid.

Epidemic events from 2011 to 2017: 91

The West Nile virus is typically spread by mosquitoes. In about 80% of infections people have few or no symptoms. About 20% of people develop a fever, headache, vomiting, or a rash, and the disease can be serious and fatal. Protect yourself from mosquitoes during the summer and fall.

Epidemic events from 2011 to 2017: 57

Yellow fever is caused by a virus transmitted to humans through mosquitoes. Common symptoms are fever, muscle pain with prominent backache, headache, loss of appetite, and nausea or vomiting. While most people recover in a few days, a small number may get worse, developing jaundice (hence the name ‘yellow fever’) abdominal pain, vomiting and bleeding from the mouth, nose, eyes or stomach. Half of the patients who enter this “toxic phase” die within 7 to 10 days. Above, a cemetery in New Orleans, where outbreaks notoriously occurred in the 1800s.

Epidemic events from 2011 to 2017: 137

Zika virus is transmitted to humans through mosquitoes. The symptoms are generally mild and include fever, rash, muscle and joint pain, but infection during pregnancy is a cause of microcephaly and other congenital abnormalities in the developing fetus and newborn and can result in complications such as fetal loss, stillbirth, and preterm birth. 

Epidemic events from 2011 to 2017: 2

Nodding syndrome is a neurological condition of unknown cause. It was first documented in Tanzania in the 1960s. Typically, it affects children between the ages of 5 and 15 years, causing cognitive dysfunction, neurological deterioration, stunted growth and a characteristic nodding of the head.