22 July 2020

The Four Corners Outbreak of 1993

Posted by Shane Hanlon

This is part of a student blog series as part of the University of Pittsburgh’s Disease Ecology Class that our own Shane M Hanlon is currently teaching. Find out more about the series and read all the posts here!   

By Robin Burke

Deer Mouse (Peromyscus maniculatus). Credit: Wikipedia

In May, 1993 a 19-year old man suddenly developed shortness of breath while driving through the Four Corners region in New Mexico. He had complained of fever and muscle pain a few days before, but generally was in good health. By the time he pulled over and paramedics arrived, he had gone into respiratory failure and later died from an acute pulmonary edema in the emergency department of Gallup Indian Medical Center.  

A few weeks prior, another member of the Navajo nation had died of the same cause mysteriously. She, like the 19 year old, was previously healthy. These two cases puzzled doctors. As they investigated the two patients’ histories, more cases of sudden pulmonary edema on the Navajo reservation began cropping up. In the few days following the first discovered death, three more were identified. All patients were young, and their deaths were sudden.

News of these deaths quickly spread, causing panic. The disease was initially termed the “Navajo Flu” and Navajo and Hopi tribe members were blamed and shunned for the disease. By June, 24 more cases of the disease had been identified and 16 total people had died.

Antibodies from nine patients were tested, revealing similarities in the antibodies to those found in patients with three Hantaviruses. These results were shocking to researchers. The three Hantaviruses strains had only ever been found in eastern Asia and northern Europe, and the disease they caused, hemorrhagic fever with renal syndrome (HFRS), did not match the clinical presentation of the cases in New Mexico, which would later be termed hantavirus pulmonary syndrome (HPS). Hantaviruses existed in the Americas, but had only been found infecting rodents, not humans. PCR confirmed the hantavirus was found in Peromyscus maniculatus, the deer mouse. The virus spread through aerosolized mouse droppings. Hardly a month after the disease’s discovery, researchers had discovered a new virus and its reservoir.

At the end of the outbreak, less than 20 people had died from HPS. This wave of cases was attributed to an unusually moist winter in 1993 that led to more vegetation in the spring and thus more deer mice to a degree of 10-fold. In the 27 years since then, less than 800 people have become infected, and ~260 people have died. Though small Hantavirus outbreaks occasionally occur still, these outbreaks do not cause the same panic that the Four Corners Outbreak of 1993 did. Source:  Hantavirus Pulmonary Syndrome—The 25th Anniversary of the Four Corners Outbreak