In global health, sometimes our best friends and worst enemies are quite small. Microscopically small. Despite their modest size, microbes have served to shape the health and well-being of communities throughout history. As an epidemiologist and public health preparedness researcher, my work has often led me to focus on pathogens – those microorganisms that have the potential to cause disease in their host. The pathogens that tend to capture my attention are ones that are novel, that might be introduced or re-introduced into non-endemic regions, or that have outbreak or pandemic potential. In this post, I will provide an update on two novel viruses that have recently caused global concern, the influenza A (H7N9) virus circulating in China and the novel coronavirus that has emerged in the Middle East. But, before I do, I would like to interject some kind words for microbes, which often get a rap because of the rogue few that cause so much damage. As a recent New York Times article reminds us, the human body is mostly microbe – for every one human cell, there are approximately 10 microbes that take residence in our bodies and provide vital functions and health benefits in ways that we are just beginning to understand. Ok, now on to the bad guys…
H7N9 is not your typical “flu.” For starters, prior to March 2013, this particular influenza virus had never before been seen in humans. When it comes to pandemic potential, that is an important factor, because it means that the population has no prior immunity. Second, this virus appears to be highly pathogenic, causing death in nearly one-quarter of those who become ill. Even one case of a novel virus such as this is cause for alarm within the public heath response community. Since March 31st, when the first human infections with this virus came to Chinese officials’ attention, there have been 131 confirmed cases and 32 deaths, all contained to China. The best evidence at this time indicates that infections are primarily spread to humans through infected poultry, such as chickens and pigeons, and poultry-contaminated environments. Thankfully, the virus is not able to spread easily from person-to-person, a necessary factor for this virus to result in a pandemic. However, because influenza viruses are constantly changing it is important to remain vigilant to any viral mutations that increase transmissibility. This highly unusual situation has sparked a global response involving the Chinese government, the World Health Organization (WHO), and other governmental and non-governmental agencies throughout the world. In addition to providing updates on the clinical and epidemiologic profile of H7N9, the Chinese government and response partners have been closely monitoring the situation, looking for any changes that might indicate that the H7N9 virus has acquired a greater ability to spread from person-to-person, investigations that are carried out in the lab (virus samples are assessed for mutations known to confer transmissibility) and in the field (thousands of family members and close contacts of infected persons have been followed to monitor whether they also become ill). To halt further transmission, live-bird markets have been closed, birds have been culled, and areas decontaminated. While documented cases have not been identified in the United States, the Centers for Disease Control and Prevention (CDC) activated it’s Emergency Operations Center to handle inquiries, provide scientific and technical support, and to prepare for a global pandemic response if needed. At the time this article was written, no new cases of H7N9 had been reported since May 8th. Compared to previous weeks in April, where the number of cases continued to rise, the absence of new cases might signal some success due the control measures implemented to stop transmission, a temporary break for unknown reasons (perhaps due to the seasonality of influenza), or an abrupt end to this novel virus.
As I write this article, the public health community is also closely monitoring a second pandemic threat, a novel coronavirus (nCoV) also known as the Middle East respiratory syndrome coronavirus (MERS-CoV). While some coronaviruses cause mild illness, such as the “common cold,” others can cause severe disease, as was seen with the global outbreak of Severe Acute Respiratory Syndrome (SARS) in 2003. Since the time the novel Coronavirus was first detected in April 2012, there have been 44 laboratory-confirmed cases, including 24 deaths – a startling proportion. The majority of cases have been reported from countries in the Middle East, with the greatest number from Saudi Arabia. Other cases have occurred in Europe among individuals who had either recently travelled in the Middle East or had been in contact with someone with recent travel to that region. Unlike the transmission of H7N9, which appears to have slowed in recent reports, the number of new infections with the novel coronavirus seems to be increasing, with more than half of the 44 cases occurring in the past few weeks. It is clear that person-to-person transmission has occurred among family members (and potentially among close contacts in healthcare facilities), but much is still unknown about how this virus is spread. The reservoir and route of infection for the novel coronavirus remain unknown. The possibility of a zoonotic source and the dynamics of person-to-person transmission are currently under investigation.
Compared to some health issues that affect millions throughout the world, these emerging threats may seem small, geographically limited, even esoteric. However, pandemics can emerge slowly, and the early days may not seem noteworthy to the outside world. If we have learned anything from past experience, it is that preventing novel pathogens from becoming the next pandemic requires a global effort.
The following resources were used in preparing this article. To get updated information on either of these situations, please visit:
World Health Organization:
http://www.who.int/influenza/human_animal_interface/influenza_h7n9/en/
http://www.who.int/csr/disease/coronavirus_infections/en/
Centers for Disease Control and Prevention (CDC)
http://www.cdc.gov/flu/spotlights/h7n9-cdc-response.htm
http://www.cdc.gov/coronavirus/ncv/index.html
International Society of Infectious Diseases, ProMed-mail
http://www.promedmail.org/
Center for Infectious Disease Research & Policy, University of Minnesota
www.cidrap.umn.edu/
About the author:
Jennifer Hunter is a researcher and practitioner who focuses on infectious disease epidemiology, public health preparedness and response, and public health systems. She recently completed the Doctor of Public Health (DrPH) program at UC Berkeley, and holds a Master of Public Health (MPH) in environmental health and epidemiology from Boston University School of Public Health. In July, she will begin the Epidemic Intelligence Service, a fellowship at the Centers for Disease Control and Prevention, where she will focus on healthcare associated infections.
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