Bovine spongiform encephalopathy (BSE) agent

Bovine spongiform encephalopathy in cows

Ingestion of feed containing infected sheep tissue

Changes in the rendering process

Chikungunya

Fever, arthritis, hemorrhagic fever

Bite of infected mosquito

Unknown

Crimean-Congo hemorrhagic fever

Hemorrhagic fever

Bite of an infected adult tick

Ecological changes favoring increased human exposure to ticks on sheep and small wild animals

Dengue

Hemorrhagic fever

Bite of an infected mosquito (primarily Aedes aegypti)

Poor mosquito control; increased urbanization in tropics; increased air travel

Filoviruses (Marburg, Ebola)

Fulminant, high-mortality hemorrhagic fever

Direct contact with infected blood, organs, secretions, and semen

Unknown; in Europe and the United States, virus-infected monkeys shipped from developing countries via air

Hantaviruses

Abdominal pain, vomiting, hemorrhagic fever

Inhalation of aerosolized rodent urine and feces

Human invasion of virus ecologic niche

Hepatitis B

Nausea, vomiting, jaundice; chronic infection leads to hepatocellular carcinoma and cirrhosis

Contact with saliva, semen, blood, or vaginal fluids of an infected person; mode of transmission to children not known

Probably increased sexual activity and intravenous drug abuse; transfusion (before 1978)

Hepatitis C

Nausea, vomiting, jaundice; chronic infection leads to hepatocellular carcinoma and cirrhosis

Exposure (percutaneous) to contaminated blood or plasma; sexual transmission

Recognition through molecular virology applications; blood transfusion practices following World War II (esp. in Japan)

Hepatitis E

Fever, abdominal pain, jaundice

Contaminated water

Newly recognized

Human herpesvirus 6 (HHV-6)

Roseola in children, syndrome resembling mononucleosis

Unknown; possibly respiratory spread

Newly recognized