By Barry C. Fox, M.D., University of Wisconsin
Dengue and Ebola are emerging infectious diseases that have become a big cause of concern in the contemporary times. While dengue gets transmitted through mosquito bites, Ebola is highly infectious and can get transferred through bodily fluids. As there are no global boundaries with infectious diseases, it is essential that people stay alert and aware.
The Menace of the Dengue Virus
Dengue has become important to us in the United States today because of its new environment in the Caribbean, and even rare cases moving into the Florida Keys and Texas.
The word dengue means careful in Spanish, and it may relate to the cautious movement of patients suffering from the pain in their muscles, bones and joints. The symptoms of dengue are high fever, severe headache, severe pain behind the eyes, and muscle and bone pain that last up to a week. It is often referred to as bone break fever.
A small proportion of dengue cases will progress to severe dengue, referred to as dengue hemorrhagic fever and dengue shock syndrome. Dengue epidemics occurred throughout the South Pacific in WWII, and continue through the present day. Recent studies estimate that, worldwide, roughly 400 million dengue virus infections occur each year.
This is a transcript from the video series An Introduction to Infectious Diseases. Watch it now, on Wondrium.
Dengue: The Infection and Its Vaccine
About ¼ or 100 million of dengue infected individuals will have symptoms of the disease, and the remaining infections will be either asymptomatic or subclinical. Because of overlapping symptoms, dengue is frequently misdiagnosed as malaria. It’s imperative for travelers to be aware that dengue fever is now endemic in Puerto Rico and many other popular travel destinations in Latin America and Asia.
As with other zoonotic diseases, the mosquito vector is infected with dengue when it bites a person who has the virus in their blood. It then bites others who become infected, leading to a vicious cycle. It cannot be transmitted person-to-person, though.
Current efforts are focusing on a dengue vaccine. Three of five vaccine candidates are of the live-attenuated type. Although current dengue vaccines do not offer complete protection against all four virus types, there were reductions of about 50 percent in dengue cases in clinical trials.
Learn more about how vaccines can save lives.
The Ebola Virus
Another emerging infectious disease is Ebola. There are actually five different types of Ebola virus, named after the places where they originated.
The outbreak of Ebola in 2014 in West Africa became an international crisis in a matter of weeks. This involved contiguous West African countries at first, but then hopped across oceans. Beginning in Guinea, then spreading to Sierra Leone and Liberia, over 18,000 cases have been confirmed with a death rate of over 50 percent.
Viral hemorrhagic fevers have been around in West Africa for decades, but have stayed within Africa until now. These are still RNA viruses, with Ebola part of the Filovirus family. Other virus examples in the group include Lassa fever, Rift Valley fever, and Marburg virus. Infections cause victims to bleed uncontrollably in multiple organ systems, including intestinal fluid losses that can rival cholera. Without proper and immediate medical care, death will rapidly occur.
The outbreak was so significant that governments revived a disease-fighting measure that had not been used in nearly a century, known as cordon sanitare. This means that an imaginary line is drawn around the infected area and no one is allowed to leave. This tactic was common in the medieval era of the Black Death, but had not been used since 1918 when the border between Poland and Russia was closed to stop typhus from spreading west. Centuries ago, in their most extreme form, everyone within the boundaries was left to die or survive, until the outbreak ended.
The Origin of the Virus
The Ebola virus was first discovered in 1976, in the Congo, and is named after the Ebola River in that country. Scientists aren’t exactly sure where the virus originated, but they think that fruit bats are the likely culprits. After bats were thought to be the host, Guinea implemented a ban on bat soup, which is actually a common street food. They also banned consumption of rats and monkeys.
Other animals carry the Ebola virus though, including chimpanzees, gorillas, and other monkeys. It is thought that transmission between countries is explained by the flight of bats. Scientists believe that the original method of transmission to humans was either directly from bats, or by handling infected animals that were infected by bats.
In humans, since the virus is found in body fluids like human blood, urine, and saliva, people caring for victims are particularly at risk, especially family members and health-care workers.
Learn more about what viruses like HIV and Ebola do to host cells.
The Transmission of Ebola Virus
Fortunately, it is believed that Ebola cannot be spread by airborne transmission. This is of immense significance as it helps with the containment of the virus. Yet, many healthcare workers, in spite of what was thought to be optimal protection, still caught the virus and died.
The number of viral particles in one drop of blood is more than a million times greater than HIV, which increases its capacity for contagion. This led to a huge increase in the production of protective garments, boots, masks, and gloves, known as personal protective equipment. Hospitals in the United States increased their supplies of protective gear, and provided training to first-line staff on how to put on the equipment and take the personal equipment off. Financial support from other countries allowed the purchase of similar equipment for affected countries.
This is how the Ebola wrecked havoc in the countries of West Africa and alarmed the medical fraternity around the globe.
Common Questions about Dengue and Ebola
The symptoms of dengue are high fever, severe headache, severe pain behind the eyes, and muscle and bone pain that last up to a week.
Ebola virus was first discovered in 1976, in the Congo, and is named after the Ebola River in that country.
The number of viral particles in one drop of blood of an Ebola infected person is more than a million times greater than HIV, which increases its capacity for contagion.