Compiled by Kris Hickman
Ever wonder which emerging diseases to watch? You’re not alone. Even for scientists, it’s difficult to tell which disease will be the next Ebola, or when it will happen. Many dangerous outbreaks in recent years have been both zoonotic and viral, so animal-borne viruses are a good place to look for the next one. Many diseases on this list are also zoonoses (see this tip sheet on understanding zoonoses) and caused by viruses, and all are emerging infectious diseases – or else they have the potential to re-emerge in the near future.
Cholera: Caused by a waterborne bacterium and usually transmitted by exposure to infected drinking water or bodily fluids, this deadly disease has been around a long time and always seems to come back – the ongoing cholera epidemic in war-torn Yemen has been classified as one of the worst cholera outbreaks in recent history. It has been noted that risk factors for cholera (poverty, overcrowdedness, poor sanitation) appear similar to the consequences of war, so look for cholera outbreaks in conflict zones.
Viral Hemorrhagic Fevers (VHFs): This is a general term for a set of symptoms, including bleeding, caused by a family of viruses that are usually transmitted by arthropods (insects) or animals. Once the virus jumps from animals to humans, the disease is highly infectious. The VHF family includes:
- Crimea-Congo Hemorrhagic Fever (CCHF): Transmitted by ticks, livestock animals, and some birds, such as ostriches. Human-to-human transmission occurs via close contact with bodily fluids. Endemic (below the 50th Parallel North) to Asia, Africa, the Balkans, and the Middle East. Fatality rate of almost 40 percent.
- Ebola: This is the most familiar of the VHFs. The case fatality rate is almost 50 percent.
- Lassa: It is transmitted to humans by rodent urine or feces. Endemic to some countries in West Africa. The case fatality rate is comparably low (less than 15 percent).
- Marburg: It is transmitted to humans via monkeys or fruit bats, and transmitted between humans via bodily fluids. Case fatality rates vary wildly (25 to 80 percent) depending on region and circumstance.
MERS: This viral respiratory disease is thought to be transmitted to humans by camels. After that, human-to-human transmission requires close contact. MERS merged in Saudi Arabia in 2012. Case fatality rate is uncertain but thought to be 35 percent or lower.
Nipah: This viral disease emerged in Malaysia in 1998. Fruit bats carry the virus and can transmit it to humans; people in Bangladesh became infected in 2004 when they ate palm sap that had been contaminated by the bats. Pigs can also act as the intermediate host for the virus. Human-to-human transmission has been seen in hospital settings. Though a case of Nipah has never occurred in the United States, a 2011 movie “Contagion,” dramatized what could happen if the virus did spread to the U.S.
West Nile virus: This virus is transmitted by mosquitoes and has been reported in all 48 of the continental United States. It can cause severe flu-like symptoms. Less than one percent of cases develop into a serious and possibly fatal illness.
Zika virus: This virus is transmitted by mosquitoes and has flu-like symptoms, with specific negative effects on pregnant women and their unborn babies.
