A
resurgence of Ebola Virus Disease in West
Africa earlier this year has struck terror within the
global community. As of 6 September 2014, the
disease has caused 3707 suspected cases, 2106
laboratory confirmed cases and 1848 deaths
[1]
.
The severity of this outbreak marks it as the largest
in history, surpassing even the first Zaire ebolavirus
(EBOV) outbreak in 1976. EBOV also happens to be
responsible for the current outbreak.
Ebolaviruses belong to the filoviridae family.
Filoviruses cause hemorrhagic fever in humans and
other primates. Out of the five ebolavirus species,
EBOV is the deadliest strain and has a mortality
rate as high as 90%
[2]
. The virus does not transmit
through airborne routes. Instead, it is spread
through contact with infected bodily fluids. Patients
typically show symptoms and become infectious
between 2 to 21 days
[1]
.
In dealing with infectious disease outbreaks,
epidemiologists often rush to identify “Patient
Zero.” Patient Zero is someone who contracts the
virus and introduces it to the human population.
By tracking down Patient Zero, epidemiologists
are able to map viral transmission, identify those
at risk, and prevent further spread of the disease.
In addition, Patient Zero is critical in providing
information about mutations throughout the
virus’ evolutionar y histor y. Genomic data thus
allows scientists to develop the most up-to-date
treatments and diagnostic tests
[3]
.
To trace Ebola back to Patient Zero, a group
of scientists investigated the initial outbreak in
Guéckédou in March. Samples from 20 patients
w i th Ebo l a - l i ke s ymptoms we re taken and
examined for the virus in their blood. The viral
genome was then analysed and sequenced,
along with any available hospital records. Data
from this analysis was able to assist scientists in
identifying a 2-year-old as Patient Zero
[4]
. This
child is suspected to have spread the disease to
his family and to a health care worker, who then
further brought it to neighbouring regions.
In addition, scientists have a theory that fruit
bats are potential virus reservoirs for Ebola. This
theor y is especially plausible as one fruit bat
species, Myonycteris torquata, has a large enough
population range to cover both Central Africa,
the source of EBOV, as well as Guinea, the origin
of this current outbreak
[5]
. However, whether or
how an infected fruit bat came into direct contact
with Patient Zero remain a mystery. It has been
proposed that intermediate hosts such as non-
human primates were involved.
No vacc i nes o r cu res have unde rgone
succes s f u l c l i n i ca l t r i a l s , but a th ree - dose
treatment of an antibody cocktail called ZMapp
administered to Ebola infected monkeys has
had promising results. A human cl inical tr ial
scheduled to begin in 2015 will provide more
information regarding the effectiveness and
dosage requirement of ZMapp. Further analysis
of the viral genomic data will be required in the
characterisation and successful treatment of Ebola
Virus Disease.
Patient Zero: Ebola
指示病例：伊波拉
