Why I am going to Liberia

10/28/2014 Update: I will be going to Sierra Leone instead of Liberia.

I suspect that many people who know me know some of the reasons I have chosen to work in the Ebola response in Liberia; I fell in love with Africa and its people during my first trip to the continent in the late 1980s, I became a nurse because I wanted to work in Africa, I have a passion for public health and tropical medicine, I'm Catholic, and I want to set an example for my son.

There is another reason that requires some explaining.

Basic reproduction number (R₀)

The basic reproduction number, or R₀ (pronounced "R-naught"), is the number of people who can be expected to be infected by a single person with a disease in a susceptible population (a population in which there is no immunity to the disease). For example, Fraser and colleagues (2009) estimated the R₀ for 2009 H1N1 pandemic influenza to be 1.4 to 1.6, meaning that at the beginning of the pandemic, each person infected with 2009 H1N1 could be expected to infect 1.5 other people. In the pre-vaccine era, the R₀ for measles was 12.5 to 18; each person with measles could be expected to infect up to 18 other people.

The reproduction number does not remain the same during an epidemic; it becomes R_(t), where t is time. The reproduction number decreases as the number of susceptible individuals in a population decreases through death, outmigration, or immunity. Changes in behavior can also influence the reproduction number. An important point is that epidemics end when the R_(t) is less than 1; that is, each infected person infects fewer than one person. We do not have sustained measles transmission in the U.S. because of high levels of immunity from immunization; the R₀ for measles in the U.S. is less than 1.

The World Health Organization Ebola Response Team (2014) estimated the current reproductive number for Liberia to be 1.51. The authors estimated that the number of people infected will double every 23.6 days. Meltzer et al. (CDC, 2014) estimated the doubling time for Liberia to be between 15 to 20 days.

Interrupting Ebola transmission

Ebola is transmitted through contact with the body fluids of a person who has Ebola virus disease (EVD). There are few health care facilities and few health care workers available in the affected countries to provide care for people with Ebola, so people who are sick with the disease have been cared for at home where their families are exposed and become infected. Health care facilities frequently lack supplies of personal protective equipment (PPE), so health care workers have been getting infected and some have fled out of fear of being infected. Ebola is also transmitted during traditional funeral ceremonies.

Getting a person with EVD isolated and into treatment prevents transmission to other people, which reduces the R_(t). People who survive EVD develop high levels of antibodies to the virus and are presumed to be immune to the species of the virus with which the individual was infected, reducing the R_(t). Finding people with EVD though contact tracing and getting them into isolation and treatment reduces the R_(t). Safe burial practices reduce the R_(t).

These interventions, isolating and treating people with EVD, contact tracing, and facilitating safe burial practices require personnel who are able to care for people with the disease and work with communities to change behaviors that place people at risk for infection.

That is why I'm going to Liberia.

This epidemic began as a relatively small outbreak in Guinea in December, 2013. The WHO Ebola ResponseTeam found that the reproduction number in Guinea fluctuated between March and July 2014, a time when control efforts could have quickly brought an end to this epidemic. Both the WHO Ebola Response Team and the CDC authors concluded that delays in responding to this epidemic cost lives. Soon, there could be thousands of new cases every week instead of hundreds.

Supporting health care workers

Holly has been very supportive of my decision to work in Liberia. I would not have accepted the position without her approval. I am fortunate that my colleagues at the health department have also been supportive of my decision.

According to the current CDC recommendations, health care workers who wore appropriate PPE while caring for patients with EVD are not considered to be at high risk for infection. The CDC recommends that people entering to the U.S. from countries affected by the Ebola epidemic self-monitor for fever and symptoms of EVD for 21 days (the incubation period). The CDC has not recommended isolating asymptomatic contacts of cases.

As I was writing this, the news media reported that New York Governor Andrew Cuomo and New Jersey Governor Chris Christie ordered 21 day mandatory quarantine of everyone entering those states from Guinea, Liberia, and Sierra Leone.

I have heard that doctors and nurses who return from working in West Africa are facing being furloughed for three weeks by their employers and that some health care professionals who had planned to go to West Africa to work in the Ebola response have cancelled those plans as a result.

These actions are, in my opinion, based on fear and not on objective evaluations of the risk that a health care worker will infect others in this country. Hundreds, if not thousands of expatriate health care professionals from around the world have responded to this epidemic, very few expatriate health care professionals have been infected, and none of those infected health care professionals has transmitted the virus to anyone in their home countries. I would not have decided to go to Liberia if I did not believe that my risk of being infected was negligible and the risk of me transmitting Ebola to Holly and Andrew was nonexistent.

 

 

While I understand the public's fear of this disease, I also realize that we live in a global community. The risk of Ebola importation to the U.S. and other countries outside of Africa increases with the duration of this epidemic and with the number of people infected with the virus. We have already seen the result of failure to recognize and respond to this threat; what began as a relatively small, isolated outbreak has become a multinational epidemic.

I encourage other health care professionals to consider working in West Africa to hasten the end of this epidemic. I encourage employers and politicians to provide incentives for health care professionals to work in West Africa for the sake of our global community rather than place unnecessary and poorly-considered burdens on their shoulders.

I thank my family and my colleagues at the health department for their support.

I have not yet seen my itinerary, but I am scheduled to be in Anniston, Alabama for CDC safety training November 3 – 5. I will be deployed to Liberia from there. I hope to be home for Christmas.

 

References

Centers for Disease Control and Prevention. (2014). Estimating the future number of cases in the Ebola epidemic – Liberia and Sierra Leone, 2014-2015. Morbidity and Mortality Weekly Report, 63(03), 1-14. http://www.cdc.gov/mmwr/preview/mmwrhtml/su6303a1.htm.

Centers for Disease Control and Prevention. (2014). Interim guidance for monitoring and movement of persons with Ebola virus disease exposure. http://www.cdc.gov/vhf/ebola/hcp/monitoring-and-movement-of-persons-with-exposure.html.

Fraser, C., Donnelly, C. A., Cauchemez, S., Hanage, W. P., Van Kerkhove, M. D., Déirdre, T. et al. (2000). Pandemic potential of a strain of influenza A (H1N1): early findings. Science, 324(5934), 1557-1561. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3735127.

New York Times. (October 24, 2014) Ebola facts. http://www.nytimes.com/interactive/2014/07/31/world/africa/ebola-virus-outbreak-qa.html.

Strebel, P. M., Papania, M. J., Dayan, G. H., & Halsey, N. A. (2008). Measles vaccine. In S. A. Plotkin, W. A. Orenstein, & P. A. Offit (Eds.) Vaccines, 5^th Ed. [Electronic version]. Elsevier.

White, P. J. & Enright, M. C. (2010). Mathematical models in infectious disease epidemiology. In J. Cohen, S. M. Opal, & W. G. Powderly (Eds). Infectious diseases, 3^rd Ed. [Electronic version]. Elsevier.

World Health Organization Ebola Response Team. (2014). Ebola virus disease in West Africa – the first 9 months of the epidemic and forward projections. New England Journal of Medicine, 371(16), 1481-1495. http://www.nejm.org/doi/full/10.1056/NEJMoa1411100.