05/13/2014 - 08:10

How to fight MERS and other zoonotic diseases

Laura H. Kahn

Laura H. Kahn

A general internist who began her career in health care as a registered nurse, Kahn works on the research staff of Princeton University's ...

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Middle Eastern Respiratory Syndrome (MERS), which has sickened at least 495 people, killed 141, and now popped up in the United States, has much in common with other recent outbreaks, including SARS, Severe Acute Respiratory Syndrome, which killed some 775 patients in 2002 and 2003: They can spread rapidly across borders, stir up fear in the public, and be transmitted from human to human.

The most important shared characteristic of ailments like MERS, SARS, Ebola, avian influenza, West Nile virus, and even diseases of bioterrorism like anthrax, though, is the fact that they are zoonotic: That is, they originate in animals and then spread to humans. And this fact points the way to fighting them. Only through a “One Health” approach, which treats human and animal health as all part of the same system, can they be prevented.

One Health is the simple concept that human, animal, and environmental health are linked. In practice, a One Health approach could mean having animal and human doctors share laboratories and integrating animal and human disease surveillance, which would help control zoonotic diseases in animal reservoirs, enable early outbreak detection, and prevent deadly pandemics.

The spread of MERS might have been prevented through such measures. Like SARS, it is believed to have originated in bats. The virus apparently gives camels colds, and people in close contact with the animals get sick. (Consuming raw camel milk and infected meat can encourage transmission but is not required.)

Veterinarians had been collecting camel blood as far back as 2003. Serum specimens from 151 camels collected that year in the United Arab Emirates and Europe showed that all of them had antibodies to MERS. So the virus had been circulating in camels for almost a decade before jumping to humans in the spring of 2012. But people only tend to notice zoonotic diseases after they have gotten into human populations.

Sadly, lessons from earlier epidemics went unheeded. Scientists figured out from SARS that bats were the host species that spread the virus to civet cats, which subsequently spread it to people. SARS and avian influenza prompted the World Health Organization (WHO), the Food and Agriculture Organization (FAO), and the World Organisation for Animal Health to establish an agreement to work together to monitor and address zoonotic diseases. Unfortunately, inherent problems in the system remained. The World Organisation for Animal Health is vastly underfunded and understaffed compared to the WHO and the FAO and doesn’t have the workforce to run field offices around the world. Also, the three organizations depend on countries to report to them, and in the case of animal disease, surveillance capabilities vary widely, depending on the national veterinary workforce, which may range from adequate to non-existent.

There are other historical examples from which public health authorities could have learned. For instance, in 1979 the Ukrainian city of Sverdlovsk experienced an outbreak of anthrax that killed 66 out of 77 infected people. Livestock had begun dying south of the city about a month before humans became ill. Scientists determined that the origin of the disease was anthrax spores escaping from a nearby military facility, but integrated disease surveillance might have prevented human deaths by paying more attention to the dying animals. Instead, they were ignored—as is typically the case.  

So far, MERS has spread widely in the Middle East. Most cases have appeared in Saudi Arabia, but the disease has also been found in Jordan, Kuwait, Oman, Qatar, and the United Arab Emirates. Travel-associated cases have now appeared in France, Germany, Great Britain, Greece, Italy, Malaysia, the Philippines, Tunisia, and most recently two US States, Indiana and Florida. Both US cases appeared in May in travelers arriving from Saudi Arabia. Symptoms include fever, coughing, and shortness of breath.

While the total number of deaths is, so far, tiny compared to the impact of global pandemics like AIDS or tuberculosis, the fact that the MERS epidemic curve—the rate at which transmission occurs—is picking up speed, particularly in Saudi Arabia, is cause for concern. Unlike SARS, which had an overall mortality rate of around 10 percent, MERS has a mortality rate around 30 percent. Poor infection control measures in hospitals and poor public health measures could be facilitating viral spread. The Kingdom recently removed Saudi Minister of Health Abdullah Al Rabeeah from his post without explanation; this development does not inspire confidence in the country’s public health capabilities.

In addition to reducing disease and preventing deaths, One Health could also save an enormous amount of money. Delia Grace, a veterinary epidemiologist and food safety specialist at the International Livestock Research Institute in Nairobi, Kenya, highlighted the economic and public health benefits of implementing a One Health approach in a paper published in April in the Onderstepoort Journal of Veterinary Research. She estimates that integrating medical and veterinary medical operations could save around 10 percent of the budgets of programs amenable to joint operations. In 2012, human health expenditures in developing countries totaled $521 billion, and veterinary health expenditures, which are harder to estimate, added up to between $1 and $2 billion. Based on those numbers, Grace estimates that the total savings brought about by joint services could be $2.68 billion per year.

Only One Health can address emerging zoonotic diseases in a way that saves scarce health resources as well as lives. Health authorities and governments didn’t act on the lessons of the past, but they can prepare for the future. Integrating the surveillance of human and animal illnesses could promptly identify the next novel disease that emerges from animals and reduce its likelihood of becoming a deadly global pandemic.