Viral Threats

Health experts consider pandemic risks of influenza viruses, coronaviruses
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Harvey V. Fineberg, MD, said the world is ill-prepared for a sustained pandemic, and a severe one could kill tens of millions of people.

Dr. Fineberg, the president of the Institute of Medicine of the National Academies, described severe acute respiratory syndrome as a warning sign, Middle East respiratory syndrome as a threat, and influenza as the cause of some of the most catastrophic recorded losses of human life.

Viral threas

At a meeting in March of the institute’s Forum on Microbial Threats, which acts as an advisory panel on disease issues, he was among speakers whose presentations collectively indicated that many of the countries where coronaviruses and influenza viruses emerge from wildlife—particularly birds and bats—lack the means to identify these agents in humans or animal reservoirs, increasing the risk that the viruses could cause pandemics in humans. Travel, trade, ecologic change, and urbanization are among human-source factors that increase risk.

The meeting concluded a few days prior to reports of an Ebola virus outbreak in Guinea, Liberia, and Mali that had, by April 7, been linked to approximately 180 reported cases and 110 deaths, mostly in Guinea, according to the World Health Organization. Fruit bats are considered to be Ebola’s natural host, according to the WHO.

Dr. Fineberg had been chair of a committee that developed a 2011 WHO report that indicated, in part, that the International Health Regulations, an agreement among nearly 200 countries, had helped those countries prepare for disease outbreaks in advance of the 2009 H1N1 influenza pandemic. But only 10 percent of countries that answered a WHO questionnaire indicated they had core capacities to detect, assess, and report health threats, and only 60 percent had national plans to do so.

Early detection and control

By detecting and studying viruses while they remain in wild or domesticated animals, public health authorities may be able to disrupt pathogens’ spread and evolution, providing a long-term strategy to reduce their harm, according to Dennis Carroll, PhD, director of the pandemic influenza and emerging threats unit for the U.S. Agency for International Development. He cited international efforts to monitor and contain the H7N9 influenza virus, which is carried by chickens and has caused infections and deaths among people in China but without sustained transmission among humans.

While he is pushing for improved disease surveillance, he has seen less inclination even within the U.S. government to spend on emergency capabilities for influenza.

Ralph Baric, PhD, a professor in the University of North Carolina Department of Epidemiology, said coronaviruses—which include MERS and SARS—have high frequencies of recombination, a mutation regulation system that allows rapid adaptation based on their environment and the potential to transmit among various hosts. He noted that the coronavirus responsible for porcine epidemic diarrhea has, since entering the U.S. in spring 2013, killed neonatal pigs on North American farms that have some of the best transmission barriers, and MERS, with a 40 percent mortality rate in humans, is in the same family of viruses.

Keiji Fukuda, MD, assistant general director for health security at the WHO, said public health infrastructure investments are lessening, and people are taking for granted the safety of their food and water and security from pandemics, which could have severe consequences. He also noted that the effects of HIV show the consequences of moving too slowly in response to emerging diseases, a problem that the international regulations are intended to help alleviate.

Reacting to outbreaks, pandemics

Dr. Jonathan Sleeman, director of the U.S. Geological Survey’s National Wildlife Health Center, said countries’ investments to monitor wildlife health and wildlife pathogens remain lacking, particularly in comparison with spending on public and agricultural surveillance.

“We have very good public health surveillance systems, but there’s no system right now for any ongoing, systematic collection of wildlife health data,” he said.

He wants national systems created to share wildlife data and compare them with public health data as well as efforts to reduce contact between people and animals that can share viruses, change attitudes about trade of wildlife products such as bush meat, and provide food security that would reduce the risk hunters will eat animals known to carry zoonoses. Studies involving epidemiology, ecology, drivers of emergence, and models of emergence could help prevent disease emergence, he said.

Wildlife health officials currently lack tools to manage many diseases while they remain only in wildlife populations, with some exceptions such as oral rabies vaccines, Dr. Sleeman said.

Anthony S. Fauci, MD, director of the National Institutes of Health’s National Institute of Allergy and Infectious Diseases, said preparing for pandemic threats requires substantial resources, as nobody knows when one is smoldering, although H5N1 and H7N9 influenza viruses are among candidates. And he questioned why governments seem to be more willing to spend money to protect against potential bioterrorism than on natural diseases since “the worst bioterrorist is nature.

Influenza infection is particularly difficult to prevent because of the lack of lifelong immunity following infection, antigenic drift of seasonal strains, imprecise predictions used for vaccine development, and the expensive vaccine development process, Dr. Fauci said. And preparations could remain insufficient for a pandemic, as the 2009 pandemic peaked before a vaccine was available.

The worst bioterrorist is nature.

-Anthony S. Fauci, MD, director of the National Institutes of Health’s National Institute of Allergy and Infectious Diseases

But Dr. Fauci noted the rapid pace of response to the SARS virus in 2003, when virus sequencing was performed within days and tests began on a vaccine within a year. He thinks a universal influenza A vaccine could be developed within the next decade, particularly through research into developing an immune response to the hemagglutinin stem regions, because they vary little across influenza strains.

While some presenters at the March meeting described possible benefits of developing a vaccine for camels against MERS, Dr. William B. Karesh, executive vice president for health and policy at EcoHealth Alliance and a guest at the meeting, questioned the value of such efforts when rabies, for example, has effective animal-use vaccines yet the disease kills 55,000 people annually worldwide. The WHO had received only about 200 laboratory-confirmed reports of MERS infections in humans with 86 deaths from September 2012 through March 2014.

Dr. Karesh later said he agreed with one of the responses that doing nothing would be unconscionable. But before others invest in developing new animal-use vaccines, he wants to find out what is preventing more widespread use of existing vaccines to protect people against deadly diseases such as rabies and brucellosis.

He also wants consideration given to the impact of each disease intervention and whether those efforts are priorities for the residents of the project area.