Next to death and taxes, nothing is more certain than the spread of cold and flu in American workplaces.  Guilt at leaving workloads with co-workers and fear of job loss, keep many sneezing and coughing people at their desks.  Lasting from days to weeks, airborne and surface-spread illnesses sweep through companies like wildfire, infecting immune-vulnerable, stressed, and over-worked employees.  For small businesses, multiple …