What is Ebola?

10/12/2014

What is Ebola?

Filoviridae• Ebolavirus – 5 viruses/species– Ebola (Zaire)– Sudan– Bundibugyo– Tai Forest – Reston

• Marburgvirus (single species)

• Cuevavirus

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Where Does it Come From?• Not entirely clear, but likely fruit bats are

natural Ebola virus hosts

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Where Does it Come From?

• Bats may infect other animals

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Where Does it Come From?• Any of these can infect humans

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Where Does it Come From?• Once a human is infected, human-to-human

transmission occurs

How are humans infected - 1?

• Infected fruit bats– Bats have high titres in faeces– Used as food

• Infected animals e.g. monkeys– Handling uncooked bush meat

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Bat soup: http://squathole.worldpress.com/

Bush meat: http://www.telegraph.co.uk/news/worldnews/ebola/11006343/Ebola-crisis-why-is-there-bush-meat-in-the-UK.html

How are humans infected - 2?

• Human-to-human transmission– Direct contact with blood or secretions

of infected people, including urine, faeces, vomit, spit, sweat, semen and breast milk

– Exposure to objects or environment contaminated with infected secretions

– Burial ceremonies through direct contact with the body

• Access through mucosal surface / breaks in skin / parenteral (needlestick injury)

• Healthcare workers must practice strict infection prevention and control precautions

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Signs and Symptoms

• Signs generally begin 2-21 days after contact with a person who is sick with Ebola– Most commonly 1-2 weeks,

average 11.4 days

• People infected with Ebola but who do not show signs of disease cannot spread the virus

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Signs and Symptoms

• General: (0-3 days)– Fever, headache, sore throat, chills,

weakness, tiredness• Gastrointestinal symptoms: (3-10 days)– Vomiting, diarrhoea, abdominal pain,

Hiccups • Severe symptoms (7-12 days) – Severe diarrhoea and vomiting, bleeding

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Other signs of Ebola Virus Disease

• Redness in the whites of the eyes• Rash on the trunk• Bleeding in 45% of cases (historically)– Mild: nose bleed, bruising– Severe: gastrointestinal bleeding, shock

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Timeline for how a person with Ebola becomes more infectious over time

Source: Public Health England

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Ebola and infectivity

• Ebola virus is spread among people through: – Touching body fluids of a person who is sick with or has died from Ebola – Touching or using objects contaminated with Ebola

• People infected with Ebola can only spread the virus to others once they have developed symptoms

• People with no or very mild symptoms (low-grade fever), level of virus is low and unlikely to pose a risk to others

• Once a person is unwell, all body fluids are infectious, with blood, vomit and diarrhoea being the most infectious

• Semen can remain infectious for up to three months after recovery

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Clinical illness in first 106 patients with EVD, Sierra Leone, May-June 2014 (n=106)

Schieffelin et al, NEJM, 29 Oct 2014

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What is the natural history of EVD in humans?

• Non-fatal cases– Fever for 5-9 days and then improve– Coincident with humoral antibody response– Complete recovery can take weeks

• Weakness/ arthralgias/ headaches/ hair loss

• Deaths– Mortality: 30-90%– Current outbreak:

• Case fatality rate: 70%1

• Among hospitalised cases, deaths occur on average 4.2 days after admission1

1 WHO Ebola Response Team. Ebola Virus Disease in West Africa – the first 9 months of the epidemic and forward projections. N Eng J Med 2014; 371:1481-95

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Ebola shares symptoms with many diseases!

• Malaria• Typhoid fever• Cholera• Other viral hemorrhagic fevers (e.g., Lassa)

• Most people sick with fever, vomiting, and diarrhea do not have Ebola

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Management of patientsTreatment and Vaccines

• Isolation• Ill patients require intensive supportive care• Fluids: oral rehydration if possible• No licensed vaccine available (several being tested)• No specific treatment available• New drug therapies being

evaluated

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Control in the population

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Acknowledgements

• Adapted from materials produced by:– World Health Organisation (WHO)– Centers for Disease Control and Prevention (CDC)– Nigerian Centre for Disease Control and Prevention– Public Health England– Dr Todd F Hatchette, Nova Scotia, Canada

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More Information

• Health Protection Surveillance Centrehttp://www.hpsc.ie/News/MainBody,14571,en.html

• CDChttp://www.cdc.gov/vhf/ebola/index.html

• WHOhttp://www.who.int/csr/disease/ebola/en/

• HSEhttp://www.hse.ie/eng/services/Campaigns/Ebolaupdate.html