My latest Mind and Matter column for the Wall
Street Journal:
Peter Pringle’s new book “Experiment Eleven” documents a shocking
scandal in the history of medicine, when Albert Schatz, the
discoverer of streptomycin, was deprived of the credit and the
Nobel Prize by his ambitious boss, Selman Waksman. Streptomycin was
and is a miraculous cure for tuberculosis.
Yet the near disappearance of tuberculosis from the Western
world, where it was once the greatest killer of all, owes little to
streptomycin. Mortality from TB had already fallen by 75% in most Western
countries by 1950, when streptomycin became available, and the rate
of fall was little different before and after. Scarlet fever,
pneumonia and diphtheria all declined rapidly long before their
cures were introduced.
Surprisingly, there is still disagreement about why so many
infectious diseases retreated in America and Europe after 1800. A
medical historian named Thomas McKeown made his name in the 1970s
with a book arguing that not only could medicine take
little credit until very late in the story (smallpox vaccination
aside), but that even sanitation played a small part before about
1900. Instead, he claimed, better nutrition, caused by better
farming practices, was the chief cause of better disease
resistance.
McKeown’s thesis produced a strong reaction from those who
thought his aim was political-to rebalance modern health-care from
cure to prevention-and that he had missed statistical quirks, like
the stagnation of the trend toward less disease at a time when
urban populations were booming. For example, the period 1830-1870
in Britain saw few improvements in mortality, despite rising living
standards. Living in cities certainly encouraged waterborne
diseases like typhoid and cholera that had rarely been a problem in
even the poorest villages. Public sanitation eventually did much to
change this.
The urban boom also gives a clue to TB’s rise and fall. By all
accounts, TB was not such a big killer in medieval times, when
people stayed in their small villages. It was urban crowding that
made the bacterium so successful and so virulent. In the latter
part of the 19th century, many of the urban poor either shared beds, or
took different shifts in the same bed. Though this had happened
before in the countryside, in the cities people were on the move,
coming into contact with new room-sharers. It was neither hygiene
nor nutrition that defeated TB (though both helped) so much as
better housing.
It also helped that after 1900 TB patients were often isolated
in sanatoria and that after 1950 people could be cured. All these
factors led to a fall in the “effective contact number” per
infected individual, from over 20 in 1900 to under one today. The
bacterium’s opportunities to jump to a new victim grew fewer and
fewer.
Does this mean that, in political terms, you can arguably score
the defeat of tuberculosis for the private sector, through the
improvement in housing caused by economic growth, just as you can
score the defeat of, say, cholera for the public sector, through
the building of sewers? Surely, it’s less straightforward than
that: Government drove a lot of slum clearance, while taxes
generated by private wealth paid for sewers, vaccines and
antibiotics.
With recent rapid economic growth in India, TB incidence has
halved since 1990. In Africa, too, it’s now falling slowly, albeit
after peaking at high levels. Drug resistance may slow the decline
but economic growth should mean it does not reverse.
There is another lesson: TB is unlikely to return in the West.
Resistance to streptomycin is spreading, but while that might make
some cases incurable, the economic and social conditions for TB to
spread no longer exist. America saw its lowest- ever incidence (3.6 per
100,000) in 2010.
Here’s the graph for Africa and South Asia:
