Experts explain how Russia’s terrifying plague investigation could impact Calif.

A worldwide uproar erupted this week after Russian media outlets reported a lab worker at an anti-plague facility died due to unexplained pneumonia. 

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The mysterious death and limited information from the Russian government sparked both concerns from medical experts about a potential lab leak of a deadly pathogen and international headlines about the risk of an outbreak, especially since pneumonic plague is the only form of that disease that can be transmitted from person to person.

Russian authorities have told the World Health Organization only that “no case of plague” has been registered in the area and no “high-threat” pathogens have been discovered among the woman’s contacts. With no international teams in the region to verify the information, some of the Russian government’s information has been met with skepticism. 

In a new statement on Tuesday, the WHO said it asked Russian authorities for more information about the potential plague case amid media reports of a second case of unexplained pneumonia.

Experts say nearly seven years after the rise of COVID-19, fears that another global outbreak could be brewing is understandable, especially since many people only know of the plague as the “black death” that killed an estimated 30% to 50% of Europe’s population in the 1300s. 

But experts in California stress that the plague is no longer a disease with an unknown cause and no cure. Today, the bacteria that causes the plague, called Yersinia pestis, is firmly entrenched as part of the ecosystem in parts of California and other Southwestern states, they say, and there are guidelines and protocols for how to handle infections. 

Plague can take three forms: Bubonic, the most common form, and the one that caused the black death, occurs when the bacteria attacks the lymph nodes; septicemic is when it enters the blood; and pneumonic is when the bacteria attacks the respiratory system.

In the U.S., a person with bubonic plague can end up with the pneumonic form of disease if it is untreated and it spreads into the lungs.

Only pneumonic plague can be spread via respiratory droplets from person to person. The disease is considered virtually 100% fatal if left untreated.

Dr. Matt Willis, an infectious disease expert and former public health officer for Marin County, told SFGATE that compared with seasonal flu and COVID-19, a pneumonic plague case is unlikely to cause a large outbreak.

“Plague tends to fizzle out really quickly,” he said. When looking at “the modern history of plague, it is like one case or very small clusters that die out very quickly.”

The plague was first reported in California in 1900 when rats carrying infected fleas arrived in San Francisco via ships from Asia.Since 1970, the California Department of Public Health reports there have been 46 cases of the plague, including one case resulting from an exposure outside the state. Seven cases of pneumonic plague have been reported since 1970, with six of those cases proving fatal. No person to person transmission of the plague has been documented in the state since urban outbreaks in the 1920s.

The most recent case was reported last year in South Lake Tahoe. It’s now endemic, or naturally occurring, in the foothills and mountainous areas in much of the state. The last time multiple cases were was in 2015 when two people were sickened in Yosemite National Park. 

Willis said while COVID-19, seasonal flu or measles can spread via aerosolized droplets that essentially render those viruses airborne, in pneumonic plague, it is spread via larger droplets that don’t travel as far. 

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“The risk of other people getting infected, even if you have pneumonic plague, is low, and it really requires very close contact,” he said. 

Dr. Monica Gandhi, an infectious disease expert at UC San Francisco, pointed out another key difference between the medieval plague outbreak and today: Now we have a cure.

Gandhi explained Yersinia pestis is “highly sensitive” to antibiotics, which can cure the infection. If a pneumonic plague case is detected in California, Gandhi said steps can be taken to prevent the spread, including prescribing a common broad-spectrum antibiotic to anyone exposed to the disease.

“We do give prophylactic medications for people who are exposed,” Gandhi said.

She said at this point the risk to regular Californians and Americans remains low but that the case highlights the unique dangers to researchers.

“There is a real risk to laboratory workers who work around plague,” she said. “You only have to inhale a few organisms and get really sick.”

In a statement sent to SFGATE, CDPH spokesperson Grant Boyken highlighted the protocol for the detection of a pneumonic plague case.

“The patient would be immediately isolated and treated, close contacts would be identified and given prophylactic antibiotics as indicated, and an environmental investigation would be conducted to identify and mitigate potential sources of exposure,” Boyken wrote in an email to SFGATE. “These steps would help prevent both person-to-person transmission and continued plague activity in the environment.”

Both Willis and Gandhi have one caveat about the potential for the plague to spread: It’s possible the lab worker was sickened with an altered Yersinia pestis or another unknown organism. In that case, there’s a chance of an outbreak of a more virulent plague or one that is harder to treat.

In a statement to SFGATE, the U.S. Centers for Disease Control and Prevention says it is “monitoring the situation closely with the State Department and our other interagency partners. The safety and security of U.S. citizens is our highest priority.”

Willis said he would be concerned about a potentially altered organism if he started to see indications there’s a rising number of pneumonic plague cases that were spread from person to person in the region.

“That’s something that could potentially lead to larger outbreaks, and something we would need to potentially prepare for over time,” Willis said. “But that’s hypothetical, and certainly not anything that you know Californians need to worry about now until we have more information.” 

This news story has been updated.