Ebola Biology 342

Ebola Family: Filoviridae, Genus: Ebolavirus - with five species Single stranded RNA Highly contagious, BioSafety Level 4 containment Zoonotic Disease is known as “Ebola Virus Disease” (EVD)

Ebola River, Democratic Republic of Congo Ebola was first described in Yambuku, Zaire (now Democratic Republic of Congo) in a 1976 outbreak along the Ebola River. It killed 90% of infected people. Ebola is a zoonotic pathogen infecting humans and other Great Apes. The intermediate host is believed to be fruit bats – various species occurring in Central and sub-Saharan Africa – but Ebola virus has not as yet been isolated from bats.

Fruit Bats The fruit bats (family: Pteropodidae) are believed to be the natural hosts for Ebola. Humans, gorillas, chimpanzees and monkeys become infected when contacting blood, body secretions, and organs of infected bats. Strangely, the forest antelope and porcupines have been found infected and ill or dead. It is surmised that humans become infected when eating ‘bush meat’ either infected bats or other animals sold in street markets throughout Africa.

Fruit Bats and Insectivorous Bats It has not been definitively demonstrated that bats are a reservoir host for the Ebola virus. Some bats have been shown to survive Ebola virus infections under laboratory conditions.

Great Apes Ebola is decimating great ape populations in Africa. Great Apes and humans share 98% of their genetic material. Gorillas and Chimpanzees are susceptible to most of the same diseases, e.g., measles and influenza, and Ebola Greater than 5,000 Gorillas where found dead in the Congo from Ebola after the 1997 outbreak. Mortality for gorillas is 95% Mortality for chimpanzees is 77%

Ebola Virus Ecology

Where Does Ebola Hide? The virus doesn’t survive long, or replicate except in living things –long term the virus requires a host to survive. In between outbreaks the virus appears to be gone. It can’t exist in chimpanzees or gorillas as they quickly die when infected. Virus has not yet been detected in bats though this is where most scientists today believe the virus must reside. At present scientists do not know where the virus hides during epidemic hiatus – and many are searching… A few scientists have suggested that the virus may reside in an Amblyomma tick that infests 20% of the noses of chimpanzees and are also found in human noses. Ticks can go years without feeding and it has been suggested that the Ebola virus quietly resides sequestered within ticks. Does Ebola first appear in chimps or gorillas?

Chimpanzee Nose Tick

Symptoms of Ebola Virus Disease Incubation period: 2 to 21 days post exposure. Infectious only after symptoms appear. Symptoms: Characterized by high fever, muscle pain, headache, sore throat, vomiting and diarrhea with blood, flushing of face and chest, small red or purple spots (body rash), abdominal accumulations of fluids under the skin causing swelling and eventually internal bleeding, kidney and liver impairment with jaundice, easy bruising and bleeding, oozing and bleeding gums, bleeding from ears, nose, mouth, eyes, and rectum, low blood pressure (hypotension), shock, and death. Infections range from asymptomatic (some rare cases) to rapid fatality (80 to 90% - average 83% fatality rate since 1976)

Ebola Rash & Symptoms

Spread of Ebola Transmission: Person to person in body fluids – all fluids are highly contagious. Once a human is infected it can quickly spread to other humans. The virus spreads via direct contact with mucous membranes, blood, vomit, saliva, urine, sweat, feces, semen, and any other body secretion, via spray of droplets from sneeze into eyes, nose, mouth or to broken skin. And from fomites, i.e., contaminated surfaces of items such as bedding, clothing, or any surface contaminated with body fluids or droplets. It’s unknown how long the virus lives outside the body. A ceremonial practice of washing the bodies of dead loved ones rapidly spreads the virus between family members. Ebola is NOT transmitted through air, water, or food.

Ebola Spillover A human comes into contact with an infected wild animal such as a fruit bat, primate or other infected wild animal. People capture and kill or collect sick, dying or dead forest animals. These animals are then prepared for sale as food in street markets, called “bush meat”. Infected animals are consumed and during the process of preparation or eating become exposed to infectious fluids. Infected person next transmits the virus to family members and friends which spread the virus to others in the community. Humans, other apes, monkeys and some fruit bats can become infected and infectious with Ebola virus. The virus is not transmitted by mosquitoes or other biting insects. Ticks are being investigated…

Bush meat

Bush Meat Market in Guinea

Ebola Epidemic History Date Cases Deaths % Mortality 1976 318 280 88% 1994 52 31 60% 1995 315 350 81% 1996-1997 99 67 68% 2002 - 2004 300 241 84% 2007-2008 413 224 54% 2014 28,205 11,354 40%

Difficulties in Containment of Ebola

Difficulties in Disposal of Infected Bodies

2014 Ebola Outbreak

Ebola Timeline for 2014 Dec. 2013 -A two year old boy dies of hemorrhagic fever in Guinea – within days the boy’s mother, sister and grandmother all die. Mourners at the family funeral become infected and carry the virus to near-by villages… By March 59 people are dead from Ebola with cases in Liberia and by May Sierra Leone. By late May Ebola travels to Nigeria and WHO declares an “International Health Emergency”. Two die in Nigeria but disease is contained. By August Senegal is infected and overall death toll goes over 1,000. Riots occur in Guinea – with rumors the virus is deliberately spread. September – death toll 2,100 – Obama sends US troops to west Africa to build treatment centers – Ebola is spiraling out of control. October the death toll 4,447.

Rapid Initial Outbreak of Ebola

Eventual spread of the Ebola Virus

Ebola’s 2014 Epidemic

What Happened in Texas? On September 25th, 2014 a man from Liberia named Thomas Eric Duncan goes to Texas Health Presbyterian Hospital in Dallas, Texas. Mr. Duncan has a super high fever (103 F), serious headache and nausea, flowing mucus, abdominal pain and dizziness – he remains in the hospital for four hours infecting two nurses. Mr. Duncan is misdiagnosed with a sinus infection and runny nose, given antibiotics and sent home even after learning that he had just arrived in the US from western Africa where the Ebola epidemic was full blown. Three days later Mr. Duncan returns to the same hospital with excruciating abdominal pain, explosive bloody diarrhea, and projectile vomiting. This time doctors place him in intensive care and finally diagnose him with Ebola. Mr. Duncan dies 10 days later on October 8th. The two nurses were sick by this time and were sent to a super containment hospital specializing in hemorrhagic fever and survived their infections. Mr. Duncan’s family is quarantined and their residence, along with that of the two nurses is decontaminated. The family sues the hospital.

Ebola in the United States Mr. Duncan was the first Ebola case in the US. A health care worker with “Doctors without Borders” worked in Guinea during the epidemic was diagnosed with Ebola after returning home to the US and was treated and cared for at Bellevue Hospital in NY and survived. The two nurses from the Presbyterian Hospital were treated and cared for; one at Emory Hospital in Atlanta, Georgia and the other at NIH Clinic Center. Both nurses survived their Ebola infections. Potentially exposed persons were quarantined for 21 days. We just narrowly averted an Ebola outbreak here in the US. One nurse traveled by air just before symptoms appeared and most remarkably none of Mr. Duncan’s contacts became infected.

Ebola Outbreak as of Sept. 2015 Guinea – 3805 cases – 2533 deaths (4 new cases in Sept.) Liberia – 10,672 cases – 4808 deaths (Ebola free) Sierra Leone – 13,911 cases – 3955 deaths (Ebola free) Italy – 1 case Mali – 8 cases – 6 deaths Nigeria – 20 cases – 8 deaths Senegal – 1 case Spain – 1 case United Kingdom – 1 case United States – 4 cases – 1 death

Ebola Vaccine Inactivated Ebola virus vaccines do not promote adequate immune response to the pathogen – and remain ineffective. Viral subunits vaccine – success in non-human primates such as macaques but not effective in humans. Currently there is no licensed Ebola vaccine.