Epidemiology
Ebola haemorrhagic fever is a severe and fatal illness
caused by Ebola virus. The recent outbreak which claimed 4,500 lives and left
9,000 sufferers, originated in Gueckedou, Guinea; before spreading to Liberia
and Sierra Leone, and concentrating around remote villages in Central and West
Africa and near tropical rainforests (WHO). Tulane University virus expert Dr.
Daniel Bausch told the Voice of America that years of war and poverty make these
countries vulnerable to an outbreak. First discovered in 1976 by Professor
Peter Piot near the Ebola River what is now the Democratic Republic of the
Congo, the virus in the recent outbreak could have come from the deadliest and most
aggressive strain according to medical charity Medicins Sans
Frontieres. Prof Peter is worried that the outbreak
could last well into next year. WHO has warned there could soon be 10,000 new
cases a week.
Fruit bats as local delicacy especially three different
species of Hypsignathus monstrosus,
Epomops franqueti, Myonycteris torquata are to blame, because of detected immunoglobulin
G specific for Ebola virus in these species.
They are not the only reservoirs for Ebola but also Marburg viruses. During the dry seasons when fruit is scarce –
conditions that foster contact between animals as they compete for food, an increase
in infection amongst great apes such as gorillas and chimpanzees is triggered.
Immune function in bats also changes during these periods, for examples as a
result of food scarcity or pregnancy which would favour viral replication aided
by aggressive primate interactions (1).
Ebola virus
During the incubation period of 2 to 21 days, manifested symptoms are sudden onset of fever fatigue, muscle pain, headache and
sore throat, followed by vomiting, diarrhoea, rash, symptoms of impaired kidney
and liver function; and in some cases, both internal and external bleeding such as
oozing from the gums or blood in the stools.
Figure
1. Ebola fever symptoms (WHO) include those found in common cold such as headache and sore
throat at early stages; and severe symptoms of vomiting, rash, diarrhoea,
bleeding from eyes, nose and mouth, impaired liver and kidney only seen at
advanced stages.
28-year-old Dr. Oliver Johnson and
the brave British medic team who are working in Freetown as part of the King’s
Health Partners scheme (partnership between Guy’s and St Thomas’, King’s
College Hospital and South London and Maudsley Trusts as well as King’s College
London), said that the locals believe the disease maybe a government
conspiracy. They also describe the Ebola patients as looking healthy until their conditions deteriorate shortly before their deaths.
Ebola shares the same encoded peptide motifs for viral particle assembly after host cell replication as deadly HIV-1 virus (2). Natural selection of secondary immune response is shuffled for survival of those with best fit antibodies. Supportive care such as rehydrating
patients who have diarrhoea and vomiting can also help recovery. Even though it is
widely assumed that a person cannot contract Ebola twice, it is not
scientifically proven. However, it is known for certain that viral replication
is error-prone hence the ease of its genetic mutation; so there is still risks of relapse to certain degree. Despite relapse warning, British nurse Will Pooley
who recently recovered from Ebola has returned to work in Sierra Leone.
Another question is that why being benign for years, fruit bats could suddenly cause an Ebola outbreak? Viral mutation could take years to perfect transmission despite being error-prone in replication between bats and humans. Perhaps primate Simian virus or HIV-1 allows cross-mutation between viruses, or it could simply be a government conspiracy. There is no definite answer. The urge now lies in vaccine.
Vaccine
Treating patients with serum injected from survivors
during the 1995 outbreak offer one solution. Further trials of prototypes will start
soon and potential vaccines maybe available in 2016. The challenge rises when
pharmaceutical companies are un-interested to invest on the vaccine which will
only be used occasionally in small number of people. Indeed, UK pharmaceuticals
firm GlaxoSmithKline and WHO had mutual decision on not to accelerate the
development of the Ebola vaccine and decided to “watch very closely”, so Dr
Ripley Ballou, head of GSK’s Ebola vaccine research, said full data on its
safety and efficacy would not be ready until late 2015, which will be too late
for the epidemic. Clinical trial of 10 years will have to be compressed into 12
months, there have already been volunteer, Nick Own, who was injected at the
centre for Vaccinology and Tropical Medicine in Oxford and will have regular
check-ups for the next six months. Well, by the time vaccines are available,
the virus might have been mutated, and just how effective the vaccine is just
depends on the speed of mutation and what kind of mutation(s) it is.
Other effort to eradicate the
disease is worth praising. Some US laboratories such as Arizona State
University (3) are already established in Ebola research and vaccine. Huge
gifts also seen from American billionaires, listing: $50 mil from Bill &
Melinda Gates Foundation, $11.9 million from Microsoft Paul Allen’s foundation,
$25 million from Facebook Mark Zuckerberg and his wife Priscilla Chan to
Centers for Disease Control and Prevention, WHO, and the US Fund for UNICEF. World
Health Organization in Birmingham UK current research is on convalescent plasma
therapy.
Canada is fast-tracked as the
country has already shipped 800 vials of vaccines to WHO which is the result of
decade of research at the Public Health Agency of Canada’s main laboratory in
Winnipeg. The vaccine had shown ‘very promising results in animal research’.
Despite no any Ebola cases in Canada, the Canadian government pledged a total
of 65 million Canadian dollars through the Red Cross and other humanitarian
agencies in the global fight against the spread of Ebola. And the Russian
project is planning to do the same. The Canadian
pharmaceutical company that also make experimental vaccines is Tekmira. Its Sarepta
therapeutics an RNA-based therapeutics is combination of two phosphorodiamidate
morpholino oligomers which target the viral matrix proteins VP24 and VP35.
How effective are current prevention?
In the UK, the only Ebola infection
isolation unit is Royal Free Hospital, London. In addition, airport screening
is not effective, especially Heathrow Airport in which screening is optional, so passengers
from Africa could easily go through. The US treats air passengers returned from Africa
with more precaution as they quarantine them all before firm diagnostics
confirm negative result.
What shall we do? Preventions are better than treatments
For Africa, avoid eating raw bush meat or contact with hosts (infected bats, monkeys, apes).
For everyone, avoid contact
with Ebola patients and their bodily fluids (WHO), do not attempt to touch
anything such as shared towels, handshakes or kisses or sexual intercourses.
Bleach and chlorine can kill Ebola. Men can still transmit the virus through
semen for up to seven weeks after recovering from Ebola.
Source
BBC,
WHO, Reuters, Centers for Disease Control and Prevention
1.Eric M. Leroy, Brice Kumulungui, Xavier Pourrut et al. Fruit bats as reservoirs of Ebola
virus. Nature Brief Communications (2005), vol 438
2. Juan Martin-Serrano et al. HIV-1 and Ebola virus encode small peptide motifs that
recruit Tsg101 to sites of particle assembly to facilitate egress. Nature
Medicine (2001) vol 7 (12).
3. Waranyoo Phoolcharoen et al. A non-replicating subunit vaccine protects mice against
lethal Ebola virus challenge. PNAS (2011), vol 108 (51): 20695-20700