Transmission and Symptoms
The Ebola virus must hide somewhere between outbreaks, but no-one has yet discovered where - it may be in monkeys or some other animal host, or it may be in healthy human carriers. Once an outbreak does occur the virus is spread from person to person via blood and bodily secretions. It can possibly infect a new victim via a cut or scratch on the skin, and can certainly do so through an injection with an unsterile needle. It can also be spread sexually.
A small number of people, although infected, do not develop serious disease. Most others, however, are susceptible to the virus and will fall ill.
The incubation period is between four and 16 days. Once inside the body the virus multiplies and invades all the major organs. There is a high fever, headache and joint pains, vomiting and diarrhoea. The characteristic haemorrhaging or bleeding is caused by a process called DIC - disseminated intravascular coagulation. Through this, the virus provokes massive clotting within the organs, and this leads paradoxically to bleeding because it uses up all the clotting factors in the blood. The clotting itself causes failure of the liver and kidneys, and this coupled with the haemorrhaging almost invariably leads to a fatal outcome.
Given that the virus is so highly contagious and virulent, it is essential to intervene rapidly in order to limit spread. Field volunteers and national staff need to be both trained and experienced so as to avoid becoming themselves infected. The activities that they undertake include the following:
- confirming the diagnosis by taking blood samples from infected persons. These samples are of course themselves highly contagious and cannot be transported - they will normally only be handled by an international team of virologists brought specifically to the site of the outbreak to investigate. The diagnosis may be initially be a presumptive one, based upon the clinical picture, and control measures must never be delayed
- active case-finding, so as to isolate infected persons in hospital contact tracing, which means finding and watching over any persons in close
- contact with a patient over the previous three weeks
- setting up of on-going epidemiological surveillance so as to track who is becoming infected and perhaps work out ways of limiting spread
- urgent education of the general public on how to avoid contagion. Such an education campaign may use all media available, including loudspeakers, radio broadcasts and dissemination of information by teachers and community leaders
- training all health staff on methods of isolation, "barrier nursing" and sterilisation, and disposal of contaminated waste
- ensuring that health facilities have adequate supplies of sterile needles and syringes, so as to be certain that they are not spreading the virus.
The Ebola virus is spread by contact with blood or other body fluids. There is currently no vaccine against it. Prevention during an epidemic relies upon reducing contact with the body fluids of infected persons:
- medical staff should wear gloves, face masks and an outer garment that is removed before they leave the hospital. Highly specialised "space suits" are not considered necessary for clinical staff
- local authorities must intervene to ensure that relatives should not handle the corpse of any persons dying of the illness, as may happen during traditional funeral preparations
- people should avoid receiving injections from untrained "village doctors" (who often have no health training whatsoever). Such people sometimes operate in local markets offering injections for a variety of ills, often using unsterilised needles and syringes
- during an outbreak people must be especially careful to wash their hands when caring for people who are sick from any cause, in case the illness is the early stage of Ebola; male survivors may secrete the virus in their semen for many weeks after they are cured and thus should refrain from unprotected sexual activity for a period of three months.