Dengue vs. Hepatitis – Part One
When I began thinking of this disease pairing, it brought to mind a story many of us learned in our childhood. I'd like to share that story again with you now:
"Once upon a time there was a hare, who bragged to anyone who would listen about how fast he could run. He took great pride in his speed, often showing off his skill and teasing those who were slower than him. During one of his bragging fits, Hare began to make fun of one of the slowest animals, Tortoise. Well, Hare bragged that he was the fastest in the world and challenged Tortoise to a race. Tortoise, who was sick of hearing Hare brag, accepted the challenge."
The Hare
Dengue fever (DF) is an arthropod-borne disease caused by one of four related viruses (DEN-1, DEN-2, DEN-3, DEN-4). The disease is found in tropical and sub-tropical regions based on the habitat of its vector, the Aedes mosquito. Humans are the primary hosts of the disease. Infection by one virus does not confer cross-immunity to the other viruses, but it does provide lifelong immunity to that particular strain; therefore, a person can theoretically be infected four separate times (e.g. one time with each form of the virus). Individuals who are infected with Dengue develop acute onset of high fever, head and muscle pain, nausea, vomiting and rash, 3-14 days after being bitten by an infected Aedes mosquito.
Dengue hemorrhagic fever (DHF) is a life-threatening complication of DF infection, which causes hemorrhage and circulatory dysfunction; in severe cases, this can progress to Dengue Shock Syndrome (DSS), characterized by serious shock and sometimes death. While classical DF infection is rarely fatal, individuals progressing to DHF and DSS experience mortality rates as high as 2.5% and 10%, respectively.
The Tortoise
Hepatitis is a condition characterized by inflammation of the liver. As such, there are many causes of hepatitis (e.g. bacteria, viruses, toxins, etc.). For our purposes, I've decided to limit our ‘Tortoise' to the five viral Hepatitis types: A, B, C, D, and E. Hepatitis A and E are acute liver diseases transmitted by fecal ingestion, contaminated water or food, and person-to-person contact (HepA). There is a vaccine available for HepA, but not HepE.
Hepatitis B and C cause chronic infection that can subsequently lead to liver disease or liver cancer. Both can be transmitted through contact with infected body fluids, sexual contact, and from mother to child during birth. While there is a vaccine for HepB, there is not one for HepC due to the extreme variability of the virus allowing it to evade the immune system. Hepatitis D requires concurrent infection with HepB; however, when this condition is met, it can cause acute, full-blown hepatitis or chronic-active hepatitis, potentially leading to cirrhosis.
Hepatitis can cause a myriad of symptoms (e.g. jaundice, vomiting, nausea, fatigue, etc.) and in its chronic form, can lead to severe liver disease (causing a variety of life-threatening symptoms) and liver cancer. The insidious nature of various forms of the disease assist with continued transmission, as does lack of availability to vaccines in poorer countries.
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