Thursday, May 14, 2015

EBOLA 101

Ebola virus disease (EVD) is a severe, often fatal illness in humans. EVD outbreaks have a case fatality rate of up to 90%. Ebola first appeared in 1976 in two simultaneous outbreaks, in Nzara, Sudan, and in Yambuku, Democratic Republic of Congo.1,2 The latter was in a village situated near the Ebola River, from which the disease takes its name. The Ebola virus is comprised of five distinct species: Bundibugyo, Ivory Coast, Reston, Sudan and Zaire. Four of the five subtypes occur in an animal host native to Africa. BDBV, EBOV, and SUDV have been associated with large EVD outbreaks in Africa, whereas RESTV and TAFV have not. Pathogenicity varies among Ebola viruses, from EBOV, which is highly lethal in humans, to RESTV, which causes disease in pigs and macaques but asymptomatically infects humans. Ebola is introduced into the human population through close contact with the blood, secretions, organs or other bodily fluids of infected animals. In Africa, infection has been documented through the handling of infected chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines found ill or dead or in the rainforest. Ebola then spreads in the community through human-to-human transmission, with infection resulting from direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other bodily fluids of infected people, and indirect contact with environments contaminated with such fluids. Burial ceremonies in which mourners have direct contact with the body of the deceased person can also play a role in the transmission of Ebola. Health-care workers have frequently been infected while treating patients with suspected or confirmed EVD. This has occurred through close contact with patients when infection control precautions are not strictly practiced. Among workers in contact with monkeys or pigs infected with Reston ebolavirus, several infections have been documented in people who were clinically asymptomatic. Thus, RESTV appears less capable of causing disease in humans than other Ebola species. Signs and symptoms. EHF is a severe acute viral illness often characterized by the sudden onset of fever, intense weakness, muscle pain, headache and sore throat. This is followed by vomiting, diarrhoea, rash, impaired kidney and liver function, and in some cases, both internal and external bleeding. Laboratory findings show low counts of white blood cells and platelets as well as elevated liver enzymes. People are infectious as long as their blood and secretions contain the virus. Ebola virus was isolated from seminal fluid up to the 61st day after the onset of illness in a laboratory acquired case. The incubation period (interval from infection to onset of symptoms) varies between 2 to 21 days. During EHF outbreaks, the case-fatality rate has varied from outbreak to outbreak between 25% and 90%. Diagnosis Differential diagnoses include, malaria, typhoid fever, shigellosis, cholera, leptospirosis, plague, rickettsiosis, relapsing fever, meningitis, hepatitis and other VHFs. Ebola virus infections can only be diagnosed definitively in the laboratory by a number of different tests: • enzyme-linked immunosorbent assay (ELISA) • antigen detection tests • serum neutralization test • reverse transcriptase polymerase chain reaction (RT-PCR) assay • virus isolation by cell culture. Tests on samples from patients are an extreme biohazard risk and should only be conducted under maximum biological containment conditions. Severe cases require intensive supportive care. Patients are frequently dehydrated and in need of intravenous fluids or oral rehydration with solutions containing electrolytes. No specific treatment or vaccine is yet available for EHF. People are infectious as long as their blood and secretions contain the virus. Men who have recovered from the disease can still transmit the virus through their semen for up to 7 weeks after recovery from illness.23 Incubation period: 2 to 21 days. Current Situation The emergence of the Ebola virus disease outbreak in Guinea, Sierra Leone and Liberia remains a serious Public Health concern.

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