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How threatened are we by Ebola virus?

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By Peter C. Doherty


The Ebola outbreak affecting Guinea, Sierra Leone, Nigeria and now Liberia is the worst since this disease was first discovered more than 30 years back. Between 1976 and 2013 there were less than 1,000 known infections. According to the Centers for Disease Control and prevention (CDC), March to 23 July 2014 saw 1201 likely cases and 672 deaths. The ongoing situation for these four West African countries is extremely dangerous, and there are fears that it could spread more widely in Africa. The relatively few intensive care units are being overwhelmed and the infection rate is likely being exacerbated by the fact that some who become ill are, on hearing that there is no specific treatment, electing to die at home surrounded by their family. The big danger is that very sick patients bleed, and body fluids and blood are extremely infectious.

American Patrick Sawyer, who was caring for his ill sister in Nigeria, has died of the disease. Working with the Christian AID Agency Samaritan’s Pulse in Monrovia, Dr Kent Brantly from Texas and Nancy Writebol from North Carolina are thought to have been infected following contact with a local staff member. Both are symptomatic but stable as I write this (July 31).

Ebola cases are classically handled by isolation, providing basic fluid support, and “barrier nursing”. Ideally, that means doctors and nurses wear disposable gowns, quality facemasks, eye protection and (double) latex gloves. That’s why it is so dangerous for patients to be cared for at home. And, even when professionals are involved, the highest incidence of infection is normally in health care workers. A number of doctors have died in the current outbreak. If there’s any suspicion that travelers returning from Africa may be infected, it is a relatively straightforward matter in wealthy, well-organized countries like the USA to institute appropriate isolation, nursing, and control. That’s why the CDC believes that the threat to North America is minimal. As for so many issues, the problem in Africa is exacerbated by poverty and the social disruption that goes with a lack of basic resources.

The fight against Ebola in West Africa...  ©EC/ECHO/Jean-Louis Mosser. EU Humanitarian Aid and Civil Protection. CC BY-ND 2.0 via European Commission DG ECHO Flickr.
The fight against Ebola in West Africa… 4 months after the first case of Ebola was confirmed in Guinea, more than 1200 people have been infected across 3 West African countries. This biggest Ebola outbreak ever recorded requires an intensification of efforts to avoid it from spreading further and claiming many more lives. Photo credits: ©EC/ECHO/Jean-Louis Mosser. EU Humanitarian Aid and Civil Protection. CC BY-ND 2.0 via European Commission DG ECHO Flickr.

Given that this disease is not a constant problem for humans, where does it hide out? Fruit bats are thought to be the natural and asymptomatic reservoir, though, unlike the hideous and completely unrelated Hendra and Nipah viruses that have caused somewhat similar symptoms in Australia and South East Asia, there is no Ebola virus in bats from those regions. And, while Hendra and Nipah are lethal for horses and pigs respectively, Ebola is killing off the great apes including our close and endangered primate relatives, the Chimpanzees and Gorillas. The few human Hendra infections have been contracted from sick horses that were, in turn, infected from fruit bats. An “index” (first contact) human Ebola case could result from exposure to bat droppings, or from killing wild primates for “bush meat” a practice that is, again, exacerbated by poverty. And, unlike Hendra, Ebola is known to spread from person to person.

The early Ebola symptoms of nausea, fever, headaches, vomiting, diarrhea, and general malaise are not that different from those characteristic of a number of virus infections, including severe influenza. But Ebola progresses to cause the breakdown of blood vessel walls and extensive bleeding. Also, unlike the fast developing influenza, the Ebola incubation period can be as long as two to three weeks, which means that there must be a relatively long quarantine period for suspected contacts. Fortunately, and unlike influenza and the hideous (fictional) bat-origin pathogen depicted in the recent movie Contagion, Ebola is, in the absence of exposure to contaminated body fluids, not all that infectious. Unlike most such Hollywood accounts, Contagion is relatively realistic and describes how government public health laboratories like the CDC operate. It’s worth seeing, and has been described as “the thinking person’s horror movie.”

Along with comparable EEC agencies and the WHO, the CDC currently has about 20 people “on the ground” in West Africa. Other support is being provided by organizations like Doctors Without Borders, the International Red Cross, and so forth. At this stage, there are no antiviral drugs available and no vaccine, though there are active research programs in several institutions, including the US NIH Vaccine Research Center in Bethesda, Maryland. Though there is no product currently available, it would be a big plus if all African healthcare workers could be vaccinated against Ebola. Apart from develop specific “small molecule” drugs, monoclonal antibodies (mAbs) that bind to proteins on the surface of the virus may be useful for emergency treatment and to give those in contact “passive” protection for three or four weeks. Such “miraculous mAbs” can now be developed and produced quickly, though they are very expensive.

What is being done? Neighboring African countries are closing their borders. International agencies and governments are providing more professionals and other resources to help with treatment and tracking cases and contacts. Global companies have been withdrawing their workers and all nations are maintaining a close watch on air travelers who are arriving from, or have recently been in, these afflicted nations.

What is this Ebola catastrophe telling us? In these days of global cost-cutting, we must keep our National and State Public Health Services strong and maintain the funding for UN Agencies like the OIE, the WHO, and the FAO. High security laboratories (BSL4) at the CDC, the NIH and so forth are a global resource, and their continued support along with the training and resourcing of the courageous, dedicated physicians and researchers who work with these very dangerous pathogens, is essential. Humanity is constantly challenged by novel, zoonotic viruses like Ebola, Hendra, Nipah, Sin Nombre, SARS, and MERS that emerge out of wildlife reservoirs, with the likelihood of such events being increased by extensive forest clearing, ever increasing population size and rapid air travel. We must be indefatigably watchful and prepared. Throughout history, nature is our worst bioterrorist.

Peter C. Doherty has appointments at the University of Melbourne, Australia, and St Jude Children’s Research Hospital, Memphis. He is the 2013 author of Pandemics: What Everyone Needs to Know, which looks at the world of pandemic viruses and explains how infections, vaccines and monoclonal antibodies work . He shared the 1996 Nobel Prize for Physisology or Medicine for his discoveries concerning “The Cellular Immune Defense”.

What Everyone Needs to Know (WENTK) series offers a balanced and authoritative primer on complex current event issues and countries. Written by leading authorities in their given fields, in a concise question-and-answer format, inquiring minds soon learn essential knowledge to engage with the issues that matter today.

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