The first thing to understand about Ebola is that we don't understand very much about Ebola.  The virus was first identified in 1976 in the blood of a Belgian nun who died of the disease, and whose job was, incidentally, giving injections to pregnant native women in the Congo, thus spreading the disease and death to many others.  Since then, sporadic small outbreaks have occurred, but active research has been sparse and desultory, complicated by the extreme hazard that a virus preparation represents, and the expensive and rigorous conditions required to study it.

The initial human infection with Ebola occurs when a human contacts the virus in nature, either by contact with the host organism, fruit bats, or by touching or ingesting contaminated meat.  Unfortunately, many old buildings in Africa are infested with bats, and it also turns out that bat soup is considered a delicacy by some.  Bushmeat, the meat of wild animals hunted and sold, is also a potential source of infection.  In past times, Ebola might wipe out a small village and disappear.  With rapid population growth and urbanization in Africa, the potential for a massive epidemic grew – and has now been realized.

The first cases in the current Ebola epidemic occurred in an area of Guinea (Guekedou) near the borders with Sierra Leone and Liberia.  Subsequently, the epidemic has spread across those borders and throughout those three countries, due to movement of infected persons.  Cultural practices, including families washing the bodies of the dead, and travel for burial in their home villages, have contributed to the spread of the epidemic, which now has infected several thousand persons.

Thus, travel of infected persons, as well as transport of bodies, has spread the epidemic to large areas, rapidly.  In this connection, it is noteworthy that the index case in the United States was a traveler from Liberia who had known he was at risk, and that the two subsequent cases included one person who traveled from Dallas to Cleveland and back, thus exposing up to 800 other  persons.  And a third Duncan contact has just turned up on a cruise ship in the Caribbean.

People travel a lot.  Obama, are you listening?

The maximum incubation period is 21 days.  False.  The 21-day period represents a statistical boundary during which 95% of infections will be detected.  Actual occurrences of infection have been observed at over 40 days (twice the  21-day interval) after initial exposure.

If you don't develop symptoms, you are not infected.  False.  A study of close contacts of infected persons, reported in Lancet in 2000, demonstrated antibodies to the Ebola virus in 11 of 24 (46%).  This is an indication that either a) these persons had become infected, but their bodies resisted development of the disease, while developing immunity, or b) these persons already had immunity from a prior encounter with the virus.  There is unfortunately no information on whether an infected but asymptomatic person can be contagiously shedding virus to others.  Neither is there any information whether some persons can become asymptomatic "carriers" for an extended period.  We do know that the carrier state occurs in the natural host organism, fruit bats.

Ebola virus is present only in bodily fluids.  False.  Viable and infectious Ebola virus may persist on surfaces, depending upon temperature, humidity, and pH, for up to 2 days (according to a specific CDC response to my inquiry).  Some speculation exists even for persistence for up to 6 days, which poses a real challenge for the airlines transporting infected persons.

Voluntary quarantines don't work very well.  True.  This has certainly been true in the U.S. experience.  The family of Duncan left their apartment several times, including sending their children to school.  A nurse with exposure flew to Cleveland and back, and a physician, Nancy Snyderman, broke quarantine to fetch a supply of her favorite soup!

Dogs can catch Ebola.  True.  Dogs that have been exposed to Ebola virus can become infected but usually do not become ill.  A study of dogs exposed in Africa showed a high rate of antibodies to the virus, indicative of past infection.  None of the animals studied carried the live virus, but a recently infected dog may shed the virus in bodily fluids, and a long-term carrier state has not been ruled out by current research.  Primates such as gorillas, chimpanzees, and monkeys may become infected, but with a high rate of lethality.

Currently, the risk to United States residents (who don't travel to epidemic areas) is vanishingly small, and not deserving of any concern for individual personal safety.   The crisis mentality that has evolved has been entirely the consequence of the stupefying ineptitude of the CDC, the real absence of any knowledge or preparation of tertiary medical facilities, and the absence of intelligent and informed leadership, combined with the arrogant political pontifications of our noble leader.  Just today, the appointment of an "Ebola czar" was announced, a role to be undertaken by a blatantly political operative with no medical knowledge.  What could go wrong?

Dr. Clark is a retired surgeon in the San Diego area.

References:

Ebola Virus Disease in West Africa — The First 9 Months of the Epidemic and Forward Projections

N Engl J Med 2014; 371:1481-1495

Human asymptomatic Ebola infection and strong inflammatory response. (Abstract)

Lancet. 2000 Jun 24;355(9222):2210-5

Ebola Virus Antibody Prevalence in Dogs and Human Risk

Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 11, No. 3, March 2005