« Prev Next »
When most children imagine something frightening they usually picture hideous monsters with sharp fangs or boogeymen lurking under their beds. Although monsters and ghouls are frightening, a lethal virus exists that I think is even scarier than any dragon or ghost: Ebola Hemorrhagic Fever.
Ebola Virus is one of the deadliest viruses known to mankind - and for good reason. With up to a 90% mortality rate, Ebola is 36 times deadlier than the influenza virus that caused the 1918 Spanish Flu Pandemic. To put that in perspective, if all 316,000,000 U.S. citizens contracted Ebola, 284,400,000 of them would be expected to die. Luckily, new groundbreaking discoveries have put mankind one step closer to developing a cure for Ebola.
Ebola was first identified in the Democratic Republic of Congo in 1976. Since its initial discovery, five strains of Ebola have been identified: Ebola Zaire, Ebola Sudan, Ebola Ivory Coast, Ebola Bundibugyo and Ebola Reston, which is only fatal to primates. All five strains can be spread through person-to-person contact while Ebola Reston (always daring to be different) can also be transmitted through the air!
The most fascinating aspects of Ebola in my opinion are its horrifying symptoms. Onset symptoms appear anywhere from 2 - 21 days after the initial infection, beginning with severe headaches, muscle aches, fever, and a sore throat. These symptoms rapidly progress into more serious ones. In the later stages of Ebola, the person exhibits severe vomiting and diarrhea, both of which often contain blood. Strangely enough, hiccups are another symptom of Ebola! Death is near when a person enters the "crash and bleed" stage whereby spontaneous eruptions of blood burst from various orifices of the body. Unfortunately, Ebola causes disseminated intravascular coagulation, which induces a shortage of blood palates and clotting factors, making it extremely difficult to stop the bleeding. The ultimate cause of death is generally shock, renal failure, or hemorrhage (CDC).
Ebola Virus has had a significant impact on the global community. To date it has taken the lives of 1, 553 people in six different countries (Democratic Republic of the Congo, Sudan, Gabon, South Africa, Uganda, and the Republic of Congo). The scientific community is actively researching Ebola in the hopes of creating a cure. One such example is a new study published by scientists at the National Institutes of Health (NIH). The NIH researchers have developed a new vaccine against Ebola that has a lot of potential. In the study by Blaney et al the researchers showed that they could make a vaccine that could protect non-human primates from Ebola virus. They made three different vaccines using a rabies virus as a platform. The rabies virus was made to express an Ebola virus glycoprotein. The rabies virus was chosen as the platform because it has already been shown to be safe and effective as a vector for vaccine production with other viruses. Also, rabies kills 24,000 people in Africa annually so a dual rabies/Ebola vaccine could be of great public health benefit.
The three test agents made were a replication competent rabies vaccine, a replication deficient rabies vaccine and a chemically inactivated rabies vaccine. All three expressed the Ebola virus glycoprotein. The vaccines were given to rhesus macaques. The animals were later injected with Ebola virus of the Mayinga strain. All three vaccines produced an immune response against both rabies and Ebola. The replication competent rabies-Ebola vaccine protected 100% of the animals. The other two vaccines protected only 50% of the animals. The researchers also showed that the protective effect was mainly from the antibody response and not so much from the cellular response. This study is an important precedent for other experimental vaccines to come. Researchers from NIH are now focusing their attention on developing an Ebola vaccine for humans and eventually creating a universal vaccine that protects against all five strains of Ebola.
Along with monkeys, pigs have also been in the spotlight recently with regards to Ebola. Ebola's natural host organism has not yet been identified, although, scientists hypothesize that the organism is a type of bat. However, a new study points to the fact that pigs, in addition to bats, may be an Ebola host. A 2009 outbreak of Ebola Reston in the Philippines shed new light on Ebola's natural host. Multiple pigs in the Philippines had tested positive for Ebola Reston and had transmitted the virus to humans. Luckily, Ebola Reston is not fatal to humans so there were no human deaths. According to the paper "Ebola Reston Virus Infection of Pigs: Clinical Significance and Transmission Potential" published in The Journal of Infectious Diseases in 2011, the discovery of Ebola Reston in pigs is significant because it "may indicate [the] emergence of a filovirus (the family of viruses Ebola belongs to) in a new mammalian host." If pigs are in fact a host of Ebola, then pig farms, and the entire pork distribution system will have to be modified for consumers' safety. But bacon lovers do not fret; you still have a few more years before scientists confirm if pigs are in fact Ebola's host organism.
For more information check out these sources:
- The Hot Zone by Richard Preston
- CDC
- WHO
- A New York Times article about a recent Ebola discovery
References:
Encyclopædia Britannica. Ebola (2012).
WHO. Ebola Haemorrhagic Fever (2012).
Centers for Disease Control and Prevention. Ebola Hemorrhagic Fever (2012).
Marsh, G., et al. Ebola Reston Virus Infection of Pigs: Clinical Significance and Transmission Potential. Journal of Infectious Diseases 204.3, (2011).
Blaney, Joseph et al. Antibody Quality and Protection from Lethal Ebola Virus Challenge in Nonhuman Primates Immunized with Rabies Virus Based Bivalent Vaccine. PLOS Pathogens (2013).
Stanford University. Tara's Ebola Site (1999).
Image credits:
1. Scott Camazine (via Encyclopædia Britannica Online )
2. Frederick A Murphy (via CDC)
