U.S. Secretary of State John Kerry has made the fierce debate on intervention in Syria irrelevant with an apparent gaffe suggesting that in order to avoid a strike, Syrian president Bashar al Assad must simply turn over his chemical weapons within a week. Russia, Syria and the United Nations all jumped on this diplomatic godsend when they saw an easy way out of the crisis, despite Kerry’s caveat that Assad “isn’t about to do it and it can’t be done.”

Ignoring the vast practical issues around regarding the decommissioning of the largest chemical weapons stockpile in the Middle East—including the challenges of accessing sites in a warzone, the fact the Organisation for the Prohibition of Chemical Weapons (OPCW) has neither the manpower nor the wherewithal to conduct such an operation, and the huge doubts over whether Assad could even be trusted to hand over his entire arsenal—even if these obstacles were to be overcome, Assad will still be left with his biological-weapons collection, most worryingly his likely access to the smallpox virus..

In July 2012, Syrian foreign minister Jihad Makdissi stated that Syria would never use chemical or biological weapons and that the Syrian military was guarding all stockpiles and sites, confirming the existence of a Syrian biological-weapons program and putting to rest years of speculation by the international community. As a result James Clapper, the U.S. Director of National Intelligence, confirmed Syria’s long-standing biological-warfare program in March 2013.

And while chemical weapons have both a treaty (Chemical Weapons Convention) and an inspection regime (the OPCW), biological weapons do not. Syria is a signatory to the Biological and Toxin Weapons Convention, but has not ratified it.

Depending on which pathogenic agent, virus or toxin was used and how it was deployed, the argument that Assad would not use biological weapons as they could endanger his government or military forces may not even be an issue for the regime. In a retaliatory strike in particular, biological weapons could be effectively released on an unsuspecting population in a geographic region that would not pose a direct health threat to Assad's government or military.

Assad's primary biological-weapon programs are run out of the SSRC (Scientific Studies and Research Centre) in Damascus, with government laboratories in Aleppo and Homs. The SSRC is a huge complex, with wings and units designated for specific pathogen research. The labs are state of the art and, unlike chemical weapons, stockpiling biological weapons is obsolete. The infrastructure to support both clandestine and legitimate research is identical, making identification of the development of biological weapons exceptionally difficult. As with vaccine development, it is only at the very end that the process becomes offensive.

Chemical weapons are calculated, while biological weapons are living organisms and do not distinguish national boundaries. Monitoring Assad's chemical-weapons stockpiles is far more transparent than locating biological programs, which are run out of both military and civilian facilities, in Syria's veterinary labs, its pharmaceutical industry, agroindustries and public-health institutes.

Smallpox is by far the most concerning program Syria likely possesses. Syria has long been suspected of retaining strains of smallpox from its last natural outbreak in 1972, as well as possibly receiving genetically modified versions from North Korea in 2006. Unlike chemical weapons, many biological-warfare agents are highly infective, transmissible, have lengthy incubation periods and are genetically modified to circumvent current medical countermeasures.

To put this threat into context, in 1972 Yugoslavia experienced one of the last outbreaks of smallpox in Europe. For each person infected, another thirteen contracted variola. Generally a 1:3 ratio is considered the norm. Yugoslavia instituted martial law, vaccinating their entire population in three weeks. Today, with modern air travel, the pace not the space is critical, and this could quickly become an international health emergency.

In light of this, it is indeed Assad's biological weapon complex that poses a far greater threat than his chemical-weapons complex. By ignoring this and letting itself become fixated on just the use of chemical weapons, the West is allowing Syria to retain a dangerous capability.

Dr. Jill Bellamy van Aalst, CEO of Warfare Technology Analytics, is an internationally recognized expert on biological warfare who develops and runs biological and nuclear war-games for EU and NATO states. Olivier Guitta is the Director of Research at the Henry Jackson Society, a foreign affairs think tank in London.