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Ebola virus and U.S. preparedness: Research on quarantines, treatments, transmission

Ebola virus particles (Wikimedia, PLoS Pathogens)Ebola virus particles (Wikimedia, PLoS Pathogens)Ebola virus particles (Wikimedia, PLoS Pathogens)
Ebola virus (Wikimedia, PLoS Pathogens)

The first U.S. case of Ebola was reported on September 25, 2014, when a man who had earlier traveled to Liberia sought help in a Dallas hospital. The U.S. Centers for Disease Control and Prevention (CDC) formally confirmed the diagnosis three days later. That patient, Thomas Eric Duncan, eventually died, and two health workers who had contact with him contracted the virus. While Ebola is contagious only when those affected are experiencing active symptoms, Duncan was sent home after an initial visit to the hospital. Further, a New York City doctor who recently returned from West Africa has also been infected.

The current outbreak of Ebola in West Africa is the deadliest in the history of the disease, with thousands of infections and deaths in Guinea, Liberia and Sierra Leone. The two latter countries could see 1.4 million cases by January 2015, according to CDC estimates. The disease was first identified in 1976, appearing simultaneously in Sudan and the Democratic Republic of Congo. Until now the number of cases has been fairly limited, but the fatality rates are high — anywhere from 25% to 90%; the average is 50% — depending on the strain of virus and the care received.

The World Health Organization has concluded that both Nigeria and Senegal appear to have stopped the spread of the disease, ending its transmission in those countries. Many top U.S. health experts say that, despite widespread fear, there remains a very low chance of an epidemic in America. Based on National Safety Council data, the Washington Post calculated that the lifetime odds of dying of Ebola in the United States are 1 in 3,934,300 — compared to 1 in 491 for a car crash, 1 in 79 for the flu and 1 in 7 for heart disease.

Quarantines and legal authority

Following policy decisions by New Jersey and New York, there remain deep questions about the efficacy of quarantines in the United States, and related legal and ethical considerations. The Congressional Research Service has published a brief on legal issues relating to screening and detaining incoming international travelers at airports, and domestic issues of quarantines. An October 2014 paper from Mark A. Rothstein at the University of Louisville, “From SARS to Ebola: Legal and Ethical Considerations for Modern Quarantine,” provides a survey of legal and ethical questions that remain unresolved:

The federal government has the constitutional authority under the Commerce Clause to impose quarantine to prevent the international and interstate spread of infection, and this responsibility has been delegated to the CDC. Nevertheless, the states maintain primary responsibility for public health, including quarantine. Many of the state quarantine laws date to the early twentieth century. The anthrax attack in 2001 provided the impetus for updating these laws to modernize and streamline state public health emergency response. Although all of the states have updated their laws, at least to some extent, these efforts must be considered works in progress. Some of the model laws used as templates for modernization have been criticized for failing to include adequate protections for civil liberties and due process. Virtually all of the laws lack key ancillary measures needed for successful quarantine, such as prohibiting employment discrimination against individuals in quarantine and providing for temporary income replacement so that individuals will not be tempted to violate the quarantine and go to work.

Past surveys of state legal policies also show variations in the scope of available powers. For more, see the following academic papers from legal scholars: “Pandemic Influenza: Ethics, Law, and the Public’s Health”; and “Public Health Versus Personal Liberty: The Uneasy Case for Individual Detention, Isolation and Quarantine.”

Treatments, therapies and new drugs

As a 2014 article in the Journal of the American Medical Association (JAMA) points out, Ebola has been around for many years now, but little progress has been made in terms of treatment: “Since 1976 more than 15 Ebola outbreaks have erupted in sub Saharan Africa, yet therapeutic options remain undeveloped. There are no licensed vaccines or specific antiviral or immune-mediated treatments for ill patients or for post-exposure prophylaxis.” An experimental drug, ZMapp, is under development, but large-scale medical trials and anything resembling wide-scale availability are far in the future — if it’s effective, which is an open question at this point. Logistical problems and a lack of funding have hampered efforts to deploy experimental drugs and vaccines, as the journal Nature notes.

The Broad Institute, jointly run by Harvard and MIT, has reported some progress in getting a fuller understanding of the genomics of the disease and its mutations, as reported in the journal Science.

While there is an urgent need to rapidly accelerate the testing of new treatments, doing so has potential downsides as well. As the University of Pennsylvania’s Dr. Steven Joffe writes, “efforts to evaluate novel agents risk diverting attention and human and material assets from proven therapeutic and public health measures. Well-motivated initiatives directed at promising new therapies must not jeopardize existing health infrastructures.”

In an October 2014 article published The New England Journal of Medicine, leading researchers note:

Even if adequate safety and immunogenicity are demonstrated in the phase 1 studies, vaccines will not be available in substantial quantity until the first quarter of 2015 at the earliest. For that to occur, funding must be secured for production. Even if an effective vaccine can be produced, it is not likely to be 100% effective, so to succeed in stemming the current outbreak, a coordinated effort to improve capacity and provide clinical care in affected countries needs to be scaled up urgently.

An October 2014 letter published in The Lancet suggests that one promising research avenue is to investigate those who appear to have an immunity to Ebola, as “many Ebola infections are asymptomatic.” The article notes that “although asymptomatic infections are unlikely to be infec­tious, they might confer protective immunity and thus have important epidemiological consequences.”

Finally, the lack of an effective drug to treat Ebola has also become a political issue. “NIH has been working on Ebola vaccines since 2001. It’s not like we suddenly woke up and thought, ‘Oh my gosh, we should have something ready here,'” Dr. Francis Collins, the head of the National Institutes of Health, has said. “Frankly, if we had not gone through our 10-year slide in research support, we probably would have had a vaccine in time for this that would’ve gone through clinical trials and would have been ready.”

Potential for a large-scale outbreak

While Ebola virus is extremely dangerous, its transmission rate is lower than that of many other diseases. “As long as people are under proper care and appropriate precautions are taken, there’s no reason to think we can’t control the transmission of the virus,” Harvard’s Michael VanRooyen has said. “So in that sense, it’s not like SARS [severe acute respiratory syndrome] or MERS [Middle East respiratory syndrome], for example, where we would worry about an epidemic spreading in the United States.”

In terms of the global spread of the disease, an October 2014 study published in The Lancet notes: “Based on epidemic conditions and international flight restrictions to and from Guinea, Liberia, and Sierra Leone as of Sept 1, 2014 (reductions in passenger seats by 51% for Liberia, 66% for Guinea, and 85% for Sierra Leone), our model projects 2·8 travellers infected with Ebola virus departing the above three countries via commercial flights, on average, every month.”

Contagiousness is measured by the average number of people whom a sick person will infect. This is strongly influenced by the specifics of each illness — when a person becomes infectious themselves after catching the disease, and how the disease can be transmitted. The transmission rate is called the disease reproduction factor and is referred to as “R0” or “R nought.”

One of the most infectious diseases is measles: In an unvaccinated population, a sick person will infect 18 others on average. (Because the vast majority of the U.S. population is vaccinated against measles, in practice its reproduction rate is effectively zero.) By comparison, the reproduction rate for mumps is 10, and that for SARS is 4. HIV is also 4, while Hepatitis C’s rate is approximately 2.

A September 2014 study in PLoS Current Outbreaks, “Assessing the International Spreading Risk Associated with the 2014 West African Ebola Outbreak,” indicates that the reproduction rate for Ebola is between 1.5 and 2. Two factors are at play: First, sick people become infectious themselves only when they begin to show symptoms. Second, direct contact is required for the disease to be transmitted. Still, because there is no vaccine against Ebola, extreme caution is warranted, and missteps by the Dallas Hospital have increased the chance that others may have been infected.

The study also models the international spreading of the outbreak — the case in Dallas was the first outside Africa — and estimates the probability of Ebola virus appearing in countries around the world. The results indicate that in the short term, the probability of international spread is “small but not negligible,” and could increase if the disease continues to advance in Africa. Countries outside Africa with the highest probability of outbreaks include the United Kingdom, Belgium and France, in part because of significant air-traffic flows.

Science and the airborne transmission hypothesis

One of the most controversial issues implicated in the current outbreak is the issue of whether Ebola can be transmitted through the air. Scientists do not believe it can, based on the most recent lab experiments. The CDC summarizes the findings of several studies as follows: “Airborne transmission of Ebola virus has been hypothesized but not demonstrated in humans. While Ebola virus can be spread through airborne particles under experimental conditions in animals, this type of spread has not been documented during human EVD outbreaks in settings such as hospitals or households.”

In terms of citations for this claim, a 2014 Nature study performed a careful test involving primates in a lab setting and did not find evidence of airborne transmission. That is the best and most recent evidence. The CDC does note two 1995 studies and a 2011 study that drew different, though not necessarily contradictory, conclusions. An October 2014 letter in The Lancet presents what is known about the need for respiratory protection.

U.S. preparedness and concerns

The United States has been planning and practicing for pandemics since the 1970s, and experts note that the “pillars” of this public health work remain basically the same: surveillance; vaccination and medical countermeasures; emergency response coordination; and communications.

For U.S. facilities to prepare for Ebola, there will need to be a variety of unique systems and protocols put into place, health experts note. A 2014 article in the Annals of Internal Medicine spells out four crucial steps: “First, staff education is vital to ‘demystifying’ Ebola and reducing anxiety; second, posters clarifying PPE [personal protective equipment] donning and doffing procedures facilitate staff understanding and compliance; and third, an ongoing, coordinated multidisciplinary effort is required to establish standard operating procedures and staff must be trained to follow them; and finally, direct observation of clinical care enforces adherence to these procedures.” However, all new systems, equipment and public health protocols carry with them the possibility of introducing new risks. Top experts on health procedures and systems say that an Ebola epidemic is preventable in the United States if strict protocols are followed.

In recent years, the CDC has warned about gaps in epidemiology capacity in state health departments; other academic survey-based research has also furnished warnings about decreased capacity. Recent crises have seen relatively successful outcomes, but they have been by no means without cost, as noted in a 2013 study in the journal Emerging Infectious Diseases:

Although the 2009 A(H1N1)pdm09 pandemic spread globally within a matter of weeks, a 1918-like pandemic did not materialize. Nonetheless, this most recent pandemic resulted in [approximately] 12,500 deaths in the United States, [approximately] 90% of which occurred in persons [younger than] 65 years of age. In the wake of this pandemic, the challenge in preparedness is to sustain the interest of private and public sectors in planning for a large-scale outbreak that may have a much more severe effect at a time that cannot be predicted.

A 2014 paper in the New England Journal of Medicine, “Pandemic Preparedness and Response: Lessons from the H1N1 Influenza of 2009,” offers deep analysis on what research and experience have revealed, and how that might influence future disease outbreaks. The author, Dr. Harvey V. Fineberg of the Institute of Medicine, notes recent “operational missteps” by the World Health Organization, and “in light of these structural impediments and operational deficiencies, the world was very fortunate that the 2009 H1N1 influenza pandemic was not more severe.”

Further resources: Also see the Congressional Research Service report “Ebola: Basics about the Disease.” Other vital sources of research-based information on the virus are The Lancet’s Ebola Research Centre, the Ebola Communication Network (USAID and Johns Hopkins Bloomberg School of Public Health) and the World Health Organization.

 

Keywords: infectious diseases, pandemics, disease outbreaks, Ebola, influenza, quarantines


    Writers: and | October 3, 2014

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