Your News feature on artificial-intelligence-enabled biological threats asks how the capability to design such threats should reshape biosecurity (see Nature 653, 344–347; 2026). Yet a biological event need not cause mass death to compromise the functional capacity of a nation. Severe and very severe ME/CFS (myalgic encephalomyelitis/chronic fatigue syndrome) provide a natural warning. People with this condition are often housebound or bedbound, dependent on care and sometimes intolerant of sensory stimulation. COVID-19 also exposed post-infectious disability at population scale. These conditions are not models of attack; they show that there is difference between survival and functional security.