Lecture 8 Flashcards
Give examples of medically important viruses
- Zaire ebolavirus (1995/1976)
- Sudan ebolavirus (1976/79)
- Reston ebolavirus (1989/92)
Marburg haemorrhagic fever
1967 - cases of haemorrhagic fever in Marburg, Germany
Lab workers infected from African Green monkey imported from Uganda
32 cases with 23 deaths
Ebola haemorrhagic fever
Simultaneous outbreaks in 1976 in DRC (318, 88%) and Sudan (284, 53%)
DRC index case is unknown
Sudan index case was cotton factory workers
Spread by contaminated needle use among family members
What was the new outbreak of virus in Uganda in 2007
Bundibugyo ebolavirus
149 cases with 37 deaths
Tai forest ebolavirus
New Ebolavirus isolated in 1994 from ethnologist who became sick whilst working in Tai Forest of Ivory Coast
Infected whilst performing necropsy on dead chimpanzee
Second seroconversion in Liberia in 1995
No deaths
Reston Ebolavirus
High mortality of Cynomolgus macaques shipped from Philippines to Reston, Virginia.
Reston Ebolavirus isolated from animals
4 humans seroconverted, no disease
Multiple subsequent exportations from Philippines
Virus detected in pigs in Philippines in 2009
Also seen in Italy, Texas and Philippines
Filovirus ecology
- Marburg virus isolated from cave-dwelling fruit bats
- Zaire ebolavirus RNA, antibodies found in three tree roosting bats (not infectious virus)
Fruit bats don’t show symptoms and hard to sample
Humans, gorillas, chimpanzees are dead-end hosts
Is there a correlation with bat populations and Ebola prevalence
- Distribution of filovirus positive (genome or antibodies) bat positive species and risk areas
- Geographical isolation of bats aligned with disease occurrence
- Immunization of hot-spot to avoid recursion
Chimps ebolavirus outbreak
Gabon (1996) - Zaire ebolavirus, 38 cases: A chimpanzee found dead in forest was eaten by hunters. 18 people who butchered the animal became ill, and ten other cases occurred in family members.
Gabon 1996-97 (Zaire ebolavirus, 60 cases) - Index case was hunter in forest camp - dead chimpanzee found in forest at the time was infected with Ebola virus.
Reservoirs and susceptibility of Ebolavirus
Reservoirs: Bats
Susceptible: Chimpanzees, Gorillas, humans and potential other species
What are the countries that have experienced the most ebola outbreaks
Republic of Congo
Uganda
Sudan
Guinea
Ivory coast
How are humans infected with ebola?
Zoonotic
Contact with animal carcass
Transmitted to humans by close contact with infected fluids
Chains of human infections are short
Reproductive index = 2
What are the different methods someone could be infected with ebola (human-to-human)
Injuries/skin abrasions
Contact with infected blood or bodily fluids from someone who is sick/dead
Contact with contaminated objects
Not by insects, water, food, or aerosol
What temperature specifically decreases Ebola virus viability
37 degrees
Recovered amount of virus significantly decreased at this temperature when investigating EDTA-whole blood, plasma, urine and stimulated capillary blood
Clinical features of Ebolavirus
Incubation period: 2-21 days
Early symptoms: fever, headache, muscle pain, diarrhoea, vomiting, muscle pain
Peak illness: rash, haemorrhage, convulsions, diffuse coagulopathy, metabolic disturbance
Impairment of vascular/coagulation systems
Replication in endothelial cells?
Tissue factor released from infected macrophages may induce coagulation irregularities
Massive blood loss
What are the multisystem involvements regarding clinical features
- Systemic (prostration)
- Gastrointestinal (anorexia, nausea, vomiting, diarrhoea, abdominal pain)
- Respiratory - Chest pain, shortness of breath, cough
- Vascular - Conjunctival injection, postural hypotension, edema
- Neurological - headache, confusion, coma
Up to 90% fatality rate in Africa
What may enhance human-to-human transmisson
Seasonal triggers of Ebola outbreak
Decades of civil unrest and human mobility
Background noise from endemic infectious diseases
Damaged infrastructure
Population motility across borders
Bad healthcare
Cultural beliefs
Traditional healer reliance
Interational air travel
