The purple plague

The first victim was a shopkeeper in Bradford. A week later, a publican in Newcastle had collapsed into a coma and later died. Inexorably, similar deaths followed, all in different parts of the country. It appeared that a new form of bacilli was involved. Where had it originated from, how had it arrived into the country, and why did it occur in such diverse places? Dubbed by the press as the 'Purple Plague', was the disease natural? OR MAN-MADE ...?