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9 of the worst viruses on Earth

By: Mary Jo DiLonardo on Dec. 9, 2019, 8:36 a.m.
nipah virus

Photo: CDC [public domain]/Wikimedia Commons

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Nipah and Rift Valley fever

The WHO recently named both these zoonotic diseases as some of the most dangerous emerging pathogens likely to cause severe outbreaks with a fatality rate as high as 75%. Nipah virus infection was first identified in 1998 when pig farmers in Malaysia became ill. More than one million pigs were euthanized as a response. In later outbreaks in India and Bagladesh, there were no obvious hosts. In 2018, the virus reappeared in India and killed 17. The virus was traced back to infected fruit bats (a natural host for the virus) in a well and rabbits being bred, reports CNN. Symptoms include respiratory issues and mental confusion.

Rift Valley fever was first identified in 1931 in sheep farmers in Kenya and has since been found in outbreaks mostly throughout Africa. The disease is transmitted by handling infected animal tissue, drinking infected milk or through the bites of infected mosquitoes. There has been no documented case of human-to-human transmission. Symptoms include fever, muscle pain and headache. A small percentage of patients get ocular disease or brain inflammation.

Neither Nipah virus infection or Rift Valley fever have vaccines.