U of T news
  • Follow U of T News

What you need to know about the Ebola virus

A Q & A with experts from the Dalla Lana School of Public Health

April 6, 2014 Ebola outbreak in Guinea (photo by by European Commission DG ECHO via Flickr)

The world is watching the outbreak of Ebola virus infection that has spread across West Africa, through the countries of Guinea, Liberia, Sierra Leone and most recently Nigeria, since early 2014. 

While the outbreak was first reported by North American sources in March, cases appear to have occurred as early as December 2013.

Several faculty, alumni and students at the Dalla Lana School of Public Health have been following the outbreak closely. Second-year Master of Public Health students Anja Bilandzic, Deepit Bhatia and Tahmina Nasserie are researching the history of Ebola outbreaks, including the current West African outbreak, while taking a course in communicable disease epidemiology with Professor David Fisman

More recently, Fisman and recent grad Edwin Khoo have been exploring the epidemiology of epidemic growth using publicly available data sources. The group sat down with Nicole Bodnar, director of communications at the Dalla Lana School of Public Health, to address questions about the ongoing Ebola outbreak.

What is Ebola and why is it so dangerous?

Ebola is a virus that can infect people and non-human primates (apes, monkeys). It is one of a group of hemorrhagic fever viruses, which can cause infection resulting in uncontrolled bleeding. These viruses are characterized by high case fatality, meaning a high percentage of infected individuals will die. It currently looks as though 60 to70 per cent of those infected with Ebola virus in the current outbreak will die, but these numbers are fluid and based on the limited information available right now. Case fatality rates often increase as outbreaks go on, since people are counted as cases days or weeks before they die.

Fortunately, Ebola is not very infectious when patients are managed by health-care personnel using appropriate personal protective items. However, based on limited information, it seems that in West Africa, cases are occurring outside health-care facilities, while nurses, doctors and others are contracting Ebola in health-care facilities as a result of being overworked, overwhelmed and unable to adhere to strict infection prevention measures.

What is the likelihood of Ebola coming to Canada?

This question is very difficult to answer, and may change over time depending on how the West African outbreak evolves. What we do know is that this is a very different outbreak from those we have seen previously, in part because the outbreak has spread to major cities with international airports (e.g., Conakry in Guinea and Lagos in Nigeria). Canada is highly connected via travel, immigration, tourism and business, and we need to be prepared for the possibility that individuals with incubating infection will arrive here and become sick in Canada.

We’ve seen some online chatter about border security and border closure with Ebola, particularly as it relates to those traveling here from countries with ongoing outbreaks. This is not a disease that could be readily screened for in airports, as the incubation period is around 12 days, which means that people can quite easily travel while feeling well, and become sick after arrival in Canada. Restricting flights from affected countries would do nothing to prevent individuals from traveling through third countries. Wide-ranging bans on travel or imports would likely be economically disastrous and achieve little.

What role do epidemiologists play in controlling the spread of Ebola and other infectious diseases?

As epidemiologists, it's our job to study the distribution (who, where, when) and determinants (why) of diseases.  We can devise data collection plans that make sure the information collected about an outbreak is meaningful, and then we have the skills to analyze those data so it's transformed from raw information to actual knowledge about what's happening. Once we have an understanding of an outbreak, we can predict what will happen next and make suggestions as to the kinds of actions that could be taken to make the outbreak slow and stop. Infectious disease epidemiologists also have additional skills, where we can use mathematical models to estimate the growth rates of epidemics. These models can allow us to hedge our bets as to where our interventions are likely to have the greatest impact, and can help us understand whether or not interventions are making a difference.

Finally, as epidemiologists, we are a key piece of the puzzle for planning and analyzing clinical trials. There are several experimental drugs and vaccines that have been proposed for use in controlling Ebola. We don't know if any of these actually do more harm than good. Epidemiologists can help ensure that rigorous, ethical and adequately powered trials of new drugs and vaccines are implemented quickly.

What impact does globalization have on Ebola spread?

Global connectedness is likely an important feature of the current Ebola outbreak that distinguishes it from prior outbreaks, which have largely occurred in small villages and towns that lacked strong connections to the outside world. Our world is now a highly connected place. With air travel, you can get to most places on Earth within 24 hours. That's much shorter than the incubation period for Ebola, and most infectious diseases. Other factors include displacement of populations (both Sierra Leone and Liberia had major civil conflicts over the last two decades, and both still have many displaced people), poverty, ecological degradation and breakdown of barriers between human and animal populations. For example, we don't know the animal reservoir of Ebola with certainty, but best evidence suggests it's fruit bats; these animals become food animals, of necessity, for impoverished people.

Disease has always traveled with the movement of populations, whether you're talking about the Black Plague in the Middle Ages, smallpox in the 18th century or SARS in 2003. In 2014 disease can simply move much faster than it could in the past.

What is the gold standard for Ebola control efforts?

Ebola is spread largely through close contact with blood and body fluids of infected people, so those most at risk have been family members, health-care providers and other caregivers, and those preparing the bodies of Ebola victims for burial. Personal protective gear (masks, goggles, gloves, protective impermeable suits) can keep health-care workers safe. It seems that several factors have combined to make the current outbreak difficult to contain: health-care workers in affected countries seem to be overwhelmed, making it difficult for them to maintain high levels of infection control; religious beliefs and traditional cultural practices related to burial of the dead have transmitted infection; and there also appears to be a level of mistrust of government and health-care systems in affected countries, which leads to non-compliance with disease control measures. It also needs to be noted that the outbreak, or more correctly, epidemic, has been growing for quite some time. Initial cases occurred in December 2013; a large outbreak had already been reported in March 2014, and we discussed this in class at that time. It is unclear whether the sudden uptick in concern relates to the extremely large numbers of infected individuals, or even to media attention resulting from the fact that westerners were returning to home countries with Ebola.

How does this Ebola outbreak compare to past outbreaks (i.e., SARS)?

Ebola and SARS are very different viruses, and different diseases, in terms of their clinical characteristics, how they're transmitted, and their ability to cause disease. SARS is a feared virus, but its case fatality rate (around 17 per cent) is far lower than that seen with Ebola. 

That said, there are some commonalities. SARS and Ebola both appear to spread in health-care environments that lack proper infection control, and both are zoonoses (diseases of animals that spread to humans) that have caused local outbreaks that did (in the case of SARS) and may (in the case of Ebola) spread globally via air travel. Both viruses may also have bats as their natural reservoir host. The fact that some populations may need to subsist on bat meat due to poverty, and that this may have contributed to the emergence of both SARS and the current Ebola outbreak, reminds us of the close connection between socioeconomic well-being and the emergence of novel infectious diseases.

If Ebola does make its way to Canada, can you predict how many people could possibly be affected? How would our public health system jump into action?

While we may see Ebola cases imported into Canada, the major impact of the current outbreak on the Canadian health-care system is likely to come in the form of scares. Toronto is very connected globally. People return from abroad with fever quite frequently and it’s often malaria or dengue fever. Now, people who develop fever after travel to West Africa may elicit Ebola-related concerns, and this has already happened. We need to remember that the risk of this disease remains extremely low in Canada.

As with SARS, it is possible that an Ebola case cared for in Canada could affect other individuals, such as health-care workers or family members. However, even in such a worst case scenario, we are unlikely to see much transmission in Canada due to the concern such an event would elicit, and the resources available to prevent spread.

In Ontario, SARS helped strengthen investment in hospital infection control, and in public health labs and agencies, and the linkages between the health-care and public health systems, such that responses to Ebola are likely to be fairly integrated. Effectively, the public health system would be responsible for overall disease control policies and interventions, surveillance and situational awareness, and providing guidance to decision-makers and the public. The focus in the health-care system will be on patient care, protection of workers and patients, and excellent infection control.

What is the Dalla Lana School of Public Health's role in working with public health bodies to prevent the spread of Ebola?

Perhaps the most important function the School plays in the context of the Ebola outbreak is to train a highly skilled and competent public health workforce capable of preventing disease transmission, and engaging in outbreak control in Canada and abroad. Many students and faculty work with global health partners, and are involved in activities that build capacity or provide health education, are engaged in research on emerging infections, or are providing expert guidance on this situation as it evolves.

Nicole Bodnar is a writer with the Dalla Lana School of Public Health at the University of Toronto.

(Read a Globe and Mail article by Jim Lavery of the Dalla Lana School of Public Health on Ebola and drug ethics; read a Toronto Star article by Ali Thompson of the Dalla Lana School of Public Health on preventing the spread of Ebola  in the Toronto Star)