The Threat No One is Talking About in Iran

The intensifying military campaign by the US and Israel has rightly focused the world's attention on nuclear proliferation, regional escalation and the potential for humanitarian catastrophe. But there is another threat – less visible and potentially more dangerous – that demands immediate international attention: what happens to a country's biological weapons programme when the state behind it is involved in active conflict?

For decades, Western intelligence agencies have assessed that Iran has pursued an offensive biological weapons capability. Despite being an early signatory to the Biological Weapons Convention – ratifying it six years before the 1979 revolution – the programme is believed to have accelerated dramatically in the late 1980s, after Iran suffered devastating chemical attacks during the Iran-Iraq War. The lesson Iranian leadership drew then was clear: never again would the country accept an asymmetry in unconventional capabilities. What followed, according to successive public intelligence assessments going back decades, was a sustained effort to develop biological agents under the cover of legitimate civilian research.

The Iranian Capablity

By the early 1990s, Iran had shifted its biological weapons research away from dedicated military sites and embedded it within civilian institutions – the Razi and Pasteur Institutes chief among them. The regime recruited former scientists from the Soviet Union's Biopreparat programme, which had been the world's largest covert biological weapons effort, to improve its arsenal. By the early 2000s, US intelligence assessments indicated that work had expanded into pharmaceutical-based agents such as fentanyl derivatives, suited to targeted operations and crowd control.

In March 2025, the US Office of the Director of National Intelligence notably hardened its language, assessing that Iran ‘very likely’ had ambitions to continue R&D of chemical and biological agents for offensive purposes. After US strikes on Iranian nuclear sites in June 2025, concerns that such capabilities could be used in retaliation have grown. In December 2025, reports emerged that the Islamic Revolutionary Guard Corps (IRGC) was working to integrate biological and chemical payloads into long-range ballistic missiles as a ‘complementary deterrent’ to its conventional missile programme.

This is precisely the type of scenario that biosecurity experts have long feared. The deliberate use of biological weapons by Iran remains unlikely, but the risk has escalated significantly since US and Israeli strikes commenced. Evidence of a warhead with a biological payload launched at foreign targets would invite catastrophic retaliation and undermine the international sympathy Tehran desperately needs, though domestic deployment to suppress an uprising or stage a false flag cannot be ruled out when decision-making shifts from strategic calculation to desperation.

Yet it is the non-deliberate risks that are the most likely in the coming weeks and months. When regimes are existentially threatened, command chains fracture. Personnel working on biological weapons programmes face powerful incentives to defect, flee or abandon their posts – particularly when they fear prosecution under international law. Biological agents require safeguarding and careful maintenance. Without both, containment can fail. The facilities reportedly housing Iran's programme are scattered across military, academic and research institutions. Many are likely dual-use sites with mixed civilian and military functions, where the line between legitimate research and weapons work has been deliberately blurred for decades.

An accidental release from any one of these facilities – whether due to damage to infrastructure, a breakdown in protocols or simple abandonment – is a realistic possibility in the coming weeks and months. So too is theft. Paramilitary factions, splinter groups or opportunistic actors may seek to seize biological agents as leverage, insurance or weapons in their own right. Whether release due to theft is accidental or deliberate matters little: transmissible pathogens do not distinguish between the two, and the epidemic consequences are the same either way.

There is also the possibility of transfer. If the regime feels under existential threat, there is a credible risk that the IRGC or its affiliates attempt to move pathogen seed stocks, stabilised agents or critical equipment or even programme scientists out of the country to allied militias in order to preserve the capability, avoid detection and prosecution or enable future operations. Transfer during a crisis multiplies the risk of loss of control.

Under-Resourced Counter-Proliferation

While the international community rightly remains vigilant about Iran's potential capabilities across the CBRN spectrum, biological weapons present a distinctive and often underappreciated danger. Unlike a nuclear device – identifiable, attributable, geographically contained in its effects – or a chemical attack, however devastating, a transmissible pathogen does not stay contained. A release of a biological agent in the region, whether through deliberate use, theft or accident, could seed an epidemic that crosses borders within days and is far harder to attribute, detect or contain.

The international community faces an urgent challenge. Securing the biological weapons infrastructure of a state under attack can be more complex than securing its nuclear programme. Nuclear facilities are large, identifiable and emit detectable radiation signatures; enrichment infrastructure cannot be hidden in a civilian laboratory. Biological agents, by contrast, are small, easily concealed and in many cases can be produced with relatively unsophisticated equipment that has entirely legitimate purposes. They are dangerous when not recognised and handled correctly. And critically, there is no biological equivalent of the International Atomic Energy Agency (IAEA) or Organisation for the Prohibition of Chemical Weapons – no standing inspectorate, no verification regime, no institutional capacity to secure facilities in a crisis. The Biological Weapons Convention operates with a support unit of just four staff and an annual budget of $2.1 million – less than a twentieth of what the IAEA spends inspecting Iran's nuclear facilities alone. The international architecture for preventing biological weapons proliferation has not been equipped for a moment like this.

There are precedents to draw upon. When the Soviet Union collapsed, the Cooperative Threat Reduction programme established in 1991 mobilised to secure an enormous and scattered arsenal of nuclear, chemical and biological weapons across fifteen newly independent states. That effort succeeded in preventing catastrophic proliferation. But it benefited from a unique moment in history, with a relatively cooperative Russian government and the absence of active military operations. Iran presents a far more volatile environment and the dual-use nature of its programme means there is no simple inventory to account for.

Several steps are needed immediately.

First, intelligence agencies and international organisations must prioritise real-time disease surveillance in and around Iran. Anomalous disease patterns may be the earliest indicator of an accidental or deliberate release.

Second, any future ceasefire framework must explicitly include provisions for the identification and securing of biological weapons-related facilities – drawing on the existing lists of implicated institutions.

Third, the international community should be preparing now for a cooperative threat reduction modelled on the Nunn-Lugar programme that secured Soviet-era weapons after 1991. This will require a multilateral coalition, however politically fraught, to help the successor regime dismantle the Iranian programme safely. Expert personnel, including those with experience in dismantling former weapon programmes, should be identified and placed on standby now.

Biological agents do not respect political timelines, and the risk of misuse, accident or transfer will not diminish on its own. The world is watching Iran's skies for missiles. It should also be watching its laboratories and public health reports.

© Cassidy Nelson, 2026, published by RUSI with permission of the authors.

The views expressed in this Commentary are the author's, and do not represent those of RUSI or any other institution.

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