Plunging cases are easy to explain. Death rates have always followed a seasonal pattern. Respiratory infection, cerebrovascular disease and frail (near death) cancer patients are all more likely to die between November and March. There is something about the winter months that makes it more likely for your blood to clot, since this disease attacks the respiratory system as well as the vascular and cold weather makes it more likely that your blot will clot, deaths from these diseases increase in winter.