Medical Examiner

Why the United States Is Plagued With Plague

The history of a racist, bungled public health battle.

earthquake and fire in San Francisco.
People standing in the rubble of collapsed buildings on Mason and Ellis Streets after the 1906 earthquake and fire in San Francisco.

Photo by Historic Photo Archive/Getty Images

In September 1908, a 10-year-old boy named Doderick Mulholland fell ill with fever and swollen glands. A dead squirrel was discovered in his Los Angeles neighborhood. Both boy and rodent were tested for plague. Both were positive.

While Doderick survived, hundreds of others who fell ill in California plague outbreaks at the turn of the 20th century did not.

The bacterium that causes plague—Yersinia pestis—might have never gained a foothold in the United States. The bacterium could have been eradicated at its source, but years of governmental delay, bureaucratic snafus, false optimism, and misguided frugality led to our current state: Y. pestis can be found in rodent populations throughout the Western half of the country.

2015 has been a busy year in the United States for human cases of plague—the very same disease that caused the Black Death in the 14th century, sporadic outbreaks across Europe for hundreds of years after that, and epidemics numbering into the hundreds of thousands of cases in India and into the millions of cases in China in the 20th century. To date, 15 cases have been diagnosed this year in the United States, three of them fatal. Several of the cases have been linked to visits to Yosemite National Park.   

Plague has been in the United States for around as long as the Ford Motor Company or the Nobel prizes have existed. The bacterium likely arrived on a steamer from our newly annexed territory of Hawaii, which was experiencing its own plague epidemic. It stowed away in rats and their fleas, jumping ship in the supposed “plague-proof” port of San Francisco. From 1900 to 1904, an epidemic of plague smoldered in the city, slow-growing but deadly, with its epicenter in the city’s Chinatown. Infected people fell ill with high fevers, headaches, and the telltale darkened swellings, or “buboes,” in their armpits and groin. By the outbreak’s end, 121 infections and 113 deaths were documented—a staggering 93 percent fatality rate, though probably inflated. Many more non-lethal cases were likely hidden from public health authorities, unidentified and uncounted.

The bubonic plague epidemic was a stain on the city and the state, threatening business and trade and increasing racial tensions among San Francisco’s citizens. Because of the prevalence of the disease in Chinatown, white residents sought and instituted drastic measures to end the plague, to the detriment of this community. A brief quarantine of the whole of Chinatown was attempted (conveniently snaking around white people’s homes and businesses, allowing them to pass in and out of the quarantined area). Death threats were levied against the man heading the plague operation, Joseph Kinyoun.

Eventually, Kinyoun was replaced by a physician named Rupert Blue who, working with his colleague Colby Rucker, was able to clean up the city. Blue’s team treated houses and streets with chlorinated lime and carbolic acid; took down dilapidated buildings and ramshackle housing additions; and trapped and poisoned rats. Eventually, these measures ended the plague epidemic. At least, they stopped the epidemic in humans.

At that time, it was not understood that plague could be maintained in the rodent population—and San Francisco’s rats were not tested for the bacterium.

Then, in 1906, the earthquake struck.

Cases began slowly appearing once again, and Rupert Blue was called back to San Francisco. This time, guided by recent discoveries that rats and their fleas spread Y. pestis to humans, rat cleanup was the primary goal, rather than quarantine. It was an enormous undertaking. More than 10 million pieces of rat bait were set, 350,000 rats trapped and killed, and 154,000 were tested for Y. pestis. The post-earthquake outbreak ended in mid-1908, tallying 160 cases and 78 deaths from around the city.  

But even as the city was celebrating its second victory against plague, cases started to appear outside of the city’s boundaries. Infected squirrels were found to the east, first in Contra Costa County, and then in Alameda County in 1909. By the middle of that year, plague was documented in rodents across 1,500 square miles of northern California. Blue wrote to his superiors in Washington, D.C. and requested an allocation of $1.50 per day to rent rifles and purchase ammunition, planning an all-out attack on the region’s squirrel population. He was denied for “sloppy form in making his request.” Eventually Rucker struck out with his own $9 rifle. Funds were eventually allocated for squirrel surveillance and elimination: $200,000 in 1912, $118,000 in 1913, and $133,000 in 1914, but as populations of squirrels declined and the percentage of those infected was lowered, the funds dried up.

A plea as late as 1941 in the American Journal of Public Health suggested that plague could still be exterminated by a “well organized and well sustained campaign throughout the entire plague area, adequately financed and probably covering a 5 year period,” at a cost of $2.5 million. By that time, plague had already spread out of California and was identified in North Dakota and Colorado.  The author, R.H. Creel, warned that “unless controlled, plague infection can be expected to extend to any city in the western states having a substantial rat population.” Like Blue’s and Rucker’s decades before him, his warnings went unheeded.

In the end, the work done by multiple teams of trappers over the decades was for naught, and may have been too late even if adequate funds and personnel had been allocated. Like the marmot and gerbil in Asia, ground squirrels, chipmunks, and prairie dogs of the Western U.S. states are now reservoirs of this bacterium, which has spread the length of California, north into Oregon and Washington, and west to the Rocky Mountains.

In Colorado, the Centers for Disease Control and Prevention at Fort Collins carries out surveillance for Y. pestis in mammals and fleas, marking trails and camping areas that have high levels of plague. Still, campers, wildlife biologists, and people living in the country or anyone else with high probability of rodent contact are at risk for contracting the infection, and a few to a dozen do so each year.

Unlike people in the Middle Ages, we have antibiotics to treat plague. If caught early, a cure is likely and death is rare. However, this year for the first time we’ve seen plague diagnosed in Georgia and Michigan (both cases in travelers who had visited areas where plague is common), and previous cases have been diagnosed in Arizona, California, Colorado, New Mexico, and Oregon. While physicians in plague-endemic areas are on the lookout for the occasional plague case, others may not immediately think of this as a possible diagnosis—and if treatment is delayed, the risk of death increases.

 We missed our window to eradicate plague in the United States. By the time we realized rodents were infected and spreading the organism, the genie was out of the bottle, and the political will necessary to marshal an elimination campaign never materialized. Agencies passed the buck trying to eliminate the organism from California squirrels, but repeatedly backed off when cases in the animals decreased—never quite able to close the deal and get the infections down to zero. After the century when we sent a man to a moon and eradicated smallpox, plague still lingers in the U.S., its fighters outwitted by the triumvirate of the flea, the rat, and the bacterium.