DEATH is almost inevitable for someone with pneumonic plague, unless the disease is diagnosed and treated early. Those who are infected struggle for each laboured breath between bouts of severe coughing which produces bloody, frothy phlegm. This is itself laden with infectious plague bacteria and so the disease is passed on.
Pneumonic plague is more infectious and more deadly than the better known bubonic plague, which kills 'only' about half of untreated victims. The pneumonic variety is spread in the infected droplets expelled during coughing, and does not require the intermediary either of rats or of fleas associated with bubonic plague.
Both diseases result from the bacterium Yersinia pestis, and both can be treated with antibiotics. Prompt treatment with streptomycin, chloramphenicol or tetracycline reduces the risk of death to less than five per cent.
The reservoir of disease is rodents in the wild, not urban rats. In recent years, outbreaks of plague have been confined mainly to Africa, South America and Southeast Asia, but there are a few cases each year even in the United States - usually hikers or campers who have been in contact with wildlife.
The infection is passed from animal to animal by their fleas, but occasionally so many wild rodents die that fleas transfer to and infect new hosts, such as rats or humans. The danger in bubonic plague is of the disease spreading to and killing large numbers of urban rats. If the fleas then transfer from dead rats to humans, an epidemic of plague results. In pneumonic plague, however, human beings themselves are the vectors of disease. In the mass exodus from Surat, Yersinia pestis will be the unseen but deadly passenger on every route out of the city.
