Sunday, October 19, 2014

An Overview on Ebola Virus Disease (EVD) Transmission

Ebola, name of a river in the Democratic Republic of Congo, in the bank of which people of a village were affected from a type of haemorrhagic fever in 1976, inadvertently got coined its' name with the disease that claimed many deaths. Simultaneously, another outbreak was also detected in Nzara, Sudan.

English: Ebola virus virion. Created by CDC mi...
English: Ebola virus virion. Created by CDC microbiologist Cynthia Goldsmith, this colorized transmission electron micrograph (TEM) revealed some of the ultrastructural morphology displayed by an Ebola virus virion. (Photo credit: Wikipedia)

The current outbreak in west Africa, starting in Guinea (first cases notified in March 2014), is the largest and most complex Ebola outbreak since the Ebola virus was first discovered in 1976.
The virus belongs to the family of Filoviridae that includes 3 genera:
  • Cuevavirus, 
  • Marburgvirus, and 
  • Ebolavirus.
There are 5 species that have been identified and named after the places of discoveries:
  • Zaire, 
  • Bundibugyo, 
  • Sudan, 
  • Reston and 
  • Taï Forest;
The first 3, Bundibugyo ebolavirus, Zaire ebolavirus, and Sudan ebolavirus have been associated with large outbreaks in Africa. The virus causing the 2014 west African outbreak belongs to the Zaire species.
Unlike some other viruses, such as influenza or SARS, Ebola virus is not spread through the air, which has been questioned recently; there has been a theoretical possibility at least.
It is not spread by water or through mosquitoes or other insects. Ebola can be spread from person to person only while the infected person is displaying symptoms. The incubation period ranges from 2 to 21 days; in an average of 8 to 10 days.
It appears that the first victim of the current Ebola outbreak in West Africa was a 2-year old boy in South-eastern Guinea, possibility coming in contact with droppings from infected bats, died in December of 2013, followed by the deaths of several members of his family.
Human to human transmission may be possible coming direct contact with saliva, semen, sweat, tears, vomits, vaginal fluid, feces, blood and used belongings of the patient; through mucus membranes of eye and mouth; through broken skin.
The virus has been isolated from semen, saliva, tears, sweat, urine, vomits, vaginal fluid and faeces of convalescent EVD patients for several days, through RT-PCR (Reverse Transcription Polymerase Chain Reaction) test for RNA.
The maximum recorded persistence of Ebola virus RNA in the blood and other body fluids of convalescent EVD patients varies by fluid type. Across combined studies (each study did not examine the exact same fluid types at the same time points), Ebola virus RNA has been detected up to 101 days after symptom onset in semen, 33 days from vaginal swabs, 29 days from rectal, 23 days from urine, 22 days from conjunctival swabs, 21 days in blood, 15 days in breast milk, eight days in saliva, and six days on skin.
Though multiple studies have shown that Ebola virus can persist in semen for longer than in blood or other body fluids, sexual transmission of Ebola has not been definitively established.
EVD among healthcare personnel and other persons is associated with direct contact with infected persons (or the bodies of persons who have died from EVD) and direct contact with body fluids from EVD patients.
CDC infection control recommendations for U.S. hospitals, including recommendations for standard, contact, and droplet precautions for general care, reflect the established routes for human-to-human transmission of EVD and are based on data collected from previous EVD outbreaks in Africa in addition to experimental data.
Airborne transmission of EVD among humans has never been demonstrated in investigations that have described human-to-human transmission although hypothetical concerns about airborne transmission of EVD have been raised.
ZMapp, a combination of three monoclonal antibodies that bind to Ebola, has been used experimentally on a few patients, and it stopped the virus in animal trials. Blood transfusion from survivors are being tried and some positive results have been obtained.
Best of preventive nursing care (Barrier Nursing) is the key to prevent the spread of the disease.
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