Scariest and deadliest viruses known to man

MANILA, Philippines - Petrifying as it might sound, Ebola is not the only deadly virus known to man. Around the globe, people die because of a wide range of different viruses, here are a few of the deadliest.

Marburg Virus Disease (MVD)
Discovery: 1967, Marburg and Frankfurt

MVD is formerly known as Marburg hemorrhagic fever. It is a  disease caused by a virus from the same family as the one that causes Ebola virus disease. According to an article in Bloomberg, an international team of virus hunters in Africa has identified a fruit bat that may be the natural host for both MVD and Ebola. MVD has a fatality rate of 90%. According to the World Health Organization (WHO), case fatality rates have varied greatly, from 25% in the initial laboratory-associated outbreak in 1967, to more than 80% in the Democratic Republic of Congo from 1998-2000 and the outbreak in Angola in 2005.

Crimean-Congo Hemorrhagic Fever (CCHF)
Discovery: 1944, Crimea;  1956, Congo

CCHF causes severe viral hemorrhagic fever outbreaks. The virus is primarily transmitted to people from ticks and livestock animals. Human-to-human transmission can occur resulting from close contact with the blood, secretions, organs or other bodily fluids of infected persons. According to WHO, CCHF outbreaks have a case fatality rate of up to 40%.

Avian Influenza
Discovery: 1878, Italy (in birds); 1997, Hongkong (in people)

Avian influenza is an infection caused by avian (bird) influenza (flu) A viruses. According to the CDC, avian influenza is very contagious among birds and some of these viruses can make certain domesticated bird species, including chickens, ducks, and turkeys, very sick and kill them. Infected birds can shed influenza virus in their saliva, nasal secretions, and feces.  The deadly form was first discovered in Italy in 1878. A 1983-84 outbreak of avian flu in Pennsylvania killed 90% of the infected birds. Most avian influenza viruses do not infect humans; however some, such as A(H5N1), A(H7N9),  and A(H1N1) have caused serious infections in people. The first known human cases of avian flu were confirmed in 1997 in Hong Kong. Pulse blog at the Milwaukee Journal Sentinel noted that in 2009, A(H1N1) death toll reached 400,000 worldwide.

Severe Acute Respiratory Syndrome (SARS)
Discovery: 2003, China, Hongkong, Vietnam

SARS is a viral respiratory illness caused by a coronavirus, called SARS-associated coronavirus (SARS-CoV). It was first reported in Asia in February 2003. According to the WHO, a total of 8,098 people worldwide became sick with SARS during the 2003 outbreak; 774 died. The virus that causes SARS is thought to be transmitted most readily by respiratory droplets (droplet spread) produced when an infected person coughs or sneezes.

Malaria
Discovery: around 1550 B.C., ancient Egyptians;  around 413 B.C., ancient Greeks

According to CDC, malaria has been noted for more than 4,000 years. Malaria is a serious disease caused by Plasmodium parasites that infects Anopheles mosquitoes which feeds on humans. If not treated within 24 hours, it can progress to severe illnesses that could lead to death. The WHO estimates that malaria caused 207,000,000 clinical episodes and 627,000 deaths, mostly among African children, in 2012. About 3.5 billion people from 167 countries live in areas at risk of malaria transmission.

Typhoid Fever
Discovery: around 430–424 B.C., Greece

Typhoid fever is a serious and potentially fatal disease caused by the bacterium Salmonella Typhi. This type of bacteria lives only in humans. People sick with typhoid fever carry the bacteria in their bloodstream and intestinal tract and transmit the bacteria through their stool. A person can get typhoid fever by drinking or eating food contaminated with Salmonella Typhi. In the United States, an estimated 5,700 cases of typhoid fever occur annually, mostly among travelers. An estimated 21 million cases of typhoid fever and 200,000 deaths occur worldwide.

Cholera
Discovery: 1563, 1870

Cholera is an acute intestinal infection caused by vibrio cholera. It has an incubation period of less than a day to five days and causes painless, watery diarrhea that quickly leads to severe dehydration and death if treatment is not promptly given. WHO says that every year, there are an estimated 3–5 million cholera cases and 100 000–120 000 deaths due to cholera.

Human Immunodeficiency Virus (HIV)
Discovery: 1980, USA

HIV is the causal agent of AIDS. It attacks the immune system, weakening a person's ability to fight infections and disease. It is typically caught through contact with blood, semen, or vaginal fluid of an HIV-positive person. According to WHO, 35.0 million people in the world are living with HIV with 2.1 million people getting newly infected by the end of 2013. HIV/AIDS still has no cure.

Sources:
World Health Organization
Centers for Disease and Prevention