In May 2015, the Pentagon publicly acknowledged that it had accidentally sent live anthrax to several labs across the United States — and to Osan Air Base in South Korea. North Korea reacted harshly. This was evidence of America’s plan to use weapons of mass destruction against their people, Pyongyang claimed in its demand for an emergency United Nations meeting. The North Koreans also resurfaced a propagandistic, ahistorical charge that American forces had already once used biological weapons against them, during the Korean War in the 1950s, when outbreaks of typhoid, cholera and smallpox gripped the nation.

Ten days after the Pentagon notice, North Korean dictator Kim Jong Un toured the newly minted Pyongyang Bio-technical Institute, posing before cameras in front of a suspiciously large pesticide production facility that analysts say has the potential to produce anthrax on a massive military scale.

In fact, experts warn that North Korea’s biological weapons could wreak as much havoc as its nuclear bombs — and are already fully developed and ready to deploy. President Trump is in the midst of a multi-country tour of Asia, with the North Korean nuclear program atop the agenda. But analysts say he would do well to make sure Pyongyang’s biological and chemical weapons are addressed as well.

“We personally haven’t seen or heard anything from the Trump administration,” Hattie Chung, a scientist and a postdoctoral fellow at Harvard University, told me. Chung co-authored a report on North Korea’s biological weapons last month that encourages increased government training of local doctors and nurses on infectious diseases to spot an outbreak before it spreads out of control.

“We think, of course, there will be certain strains that will be extremely hard to contain,” Chung said, “but if you have a strong health care system, that will make a difference.”

Pyongyang is on the verge of mastering a delivery system capable of sending a nuclear warhead to the U.S. mainland — a fast-approaching threat that has dominated press headlines because of the expected strategic consequences. Presidents from both parties have long feared that this technology would allow North Korea to force the U.S. and its allies to recognize its regime, to remove military options from the table or even to push American troops off the Korean Peninsula entirely. The very possession of this capability strikes fear in Washington, making it a strategic asset for Pyongyang.

But these other weapons of mass destruction “could have the same impact of a nuclear weapon in terms of the number of casualties,” said Andy Weber, assistant secretary of defense for nuclear, chemical and biological defense programs in the Obama administration.

Those who track the issue, including researchers and former U.S. defense officials who teamed up on the Harvard report, believe that Kim is actually more likely to deploy biological or chemical arms. These weapons are easier to produce, to deliver, to conceal and to calibrate, and their use would be less likely to trigger the same international response as a nuclear strike.

“It is possible they could be used in a pre-crisis stage,” Weber told me. “They could be delivered covertly against Seoul or against naval and air bases used for mobilization of forces onto the peninsula. And they could give Kim a degree of deniability, as it’s hard to attribute biological attacks.”

The Harvard report, put out by the Kennedy School’s Belfer Center for Science and International Affairs, details a sophisticated biological weapons program built behind closed doors by foreign-trained scientists — and warns that its opaqueness has led to a “low threat perception” in U.S. policy circles out of whack with the true extent of the danger. Other reports based on public South Korean defense assessments outline a similarly extensive and sophisticated chemical weapons program. Analysts don’t believe that North Korea has conventional long-range delivery vehicles for either of these weapons to strike the U.S. mainland, but they do believe Pyongyang can send them south — toward more than 51 million South Koreans (and thousands of American troops).

Washington and Seoul estimate that Pyongyang has 2,500 to 5,000 metric tons of weaponizable chemical agents and a minimum of 13 different biological pathogens in its possession, alongside up to 60 nuclear warheads. Among those biological and chemical arms are some of the deadliest agents and toxins known to man: anthrax, smallpox and the plague, hydrogen cyanide, mustard, sarin and VX, the deadliest of all.

Unlike nuclear weapons, which must be delivered through complex and detectable means, chemical or biological arms can be delivered covertly and with ease by mail or drone — and biological agents can even be spread by infected human agents. If Pyongyang were to use its own people as vehicles for conveying such weapons to South Korean civilians or American troops, an attack might be impossible to detect ahead of time, Chung told me.

The equivalent of a “a few bottles of wine” of anthrax could wipe out 50 percent of a major metropolitan population, according to the Harvard study. “North Korea has 200,000 special forces,” the study notes. “Even a handful of those special forces armed with (biological weapons) would be enough to devastate South Korea.”

The Pentagon has required all troops deployed in Korea to be vaccinated for smallpox and anthrax since 2004. Weber told me that U.S. and South Korean troops have markedly increased training for a biological attack over the past five years as the U.S. assessed that North Korean capabilities “changed.” At the beginning of 2017, the U.S. decided to deploy its most advanced bio-surveillance equipment to the peninsula’s largest port city.

Chemical weapons differ from their biological brethren in that they kill instantaneously and are not contagious, but they are equally as easy to deliver by either conventional or covert means. These two programs are well-concealed in North Korea and difficult to monitor, detect, measure or verify, separating them from the North’s nuclear weapons program, which can be traced through external monitoring of its missile firings and underground explosive tests.

Another reason analysts believe that Kim might resort to chemical or biological weapons: He already has. VX was the weapon of choice used in the murder of Kim’s half-brother in the middle of an international airport in February — a sign of the dictator’s willingness to use such toxins, analysts say.

There is also a different geopolitical environment when it comes to using chemical weapons. Despite the existence of long-standing international norms prohibiting their use since World War I, chemical weapons have been utilized with frequency over the past six years by Pyongyang’s close ally, Syrian President Bashar al-Assad, in that nation’s civil war. Their most deadly deployments went largely ignored by international powers, and their smaller-scale use has gone entirely unpunished.

“Korean analysts should take note of how chemical weapons were used in the Syrian civil war, because this is likely going to be a test-bed for future North Korean actions in conflict with the South,” one military strategist, Bruce Bechtol Jr., wrote in a 2015 report for the Korean Journal of Defense Analysis.

Chemical and biological weapons also provide plausible deniability for their handlers — and Kim publicly denies the very existence of the programs themselves. Russia continues to provide cover for Assad at the U.N. by denying he has had any role in their use to this day. Hydrocarbon impurities in sarin batches and endogenous strains of specific pathogens have made them slightly easier to trace back to their sources, but the science can still be questioned and politicized — unlike the origins of the ever-rare nuclear weapon.

Biological weapons in particular cause confusion, Chung said, as it is difficult for governments to conclude whether an epidemic is natural or intentional. Attribution is extremely difficult. Their use would thus provide Kim with the ability to devastate a large target population while denying responsibility for the deaths — which could help him avoid international consequences.

Biological and chemical weapons can be deployed with relative precision, depending on the strains of pathogen and agent used, according to Chung. They can be calibrated to strike fear but try to minimize casualties enough to not prompt a military response.

In other words: These are weapons of mass destruction that can potentially cause an equal toll on human life without the risks to North Korea that a nuclear attack would incur — including the possibility that the U.S. would employ regime-ending military action.