Published on:

Malaria, TB and Aids are in steady retreat

My Times column is on malaria, TB and Aids — all
in steady decline, a fact that officials and journalists seem
reluctant to report:


There’s a tendency among public officials and
journalists, when they discuss disease, to dress good news up as
bad. My favourite example was a BBC website headline from 2004 when
mortality from the human form of mad-cow disease, which had been
falling for two years, rose from 16 to 17 cases: “Figures show rise
in vCJD deaths” wailed the headline. (The incidence fell to eight
the next year and zero by 2012, unreported.) Talk about grasping at
straws of pessimism.

Last week there was a neat example of how good news is no news
in the world of public health. Newspapers widely reported a
scientific paper, which argued that malaria might get worse in the
future at high altitudes as a result of global warming allowing
mosquitoes and parasites to survive in higher regions such as
Ethiopia and Colombia. Breathlessly, the reports suggested an extra
three million people a year might catch the disease.

Did nobody stop to ponder three obvious questions to put this
claim in context? First, less than 2 per cent of Africa is too high
for malarial mosquitoes. Second, malaria’s distribution shows
little correlation with temperature anyway. Lots of tropical
countries are free of the disease and lots of cold countries,
including Britain and Arctic Russia, have in the past suffered
severe epidemics of it. And third, malaria incidence has been not
increasing as the world warms but decreasing at a rate of more than five million
cases a year for seven years.

The death toll from malaria is falling even faster than the incidence: down
by 29 per cent since the year 2000, despite a steadily rising
global population. That’s an astonishing bit of happy news about
one of humankind’s biggest killers, although 627,000 people still
died of it in 2012. One of the places that the authors of the new
study say global warming is supposed to make the problem worse at
high altitudes is South America. Yet in the whole of the Americas,
north and south, there were officially just 800 deaths from malaria
in 2012.

In short, the future of malaria depends on bed nets, mosquito
control, anti-malarial drugs, better housing and Bill Gates.
Temperature is all but irrelevant. Fascinatingly, a statistical
study published last year explained not only the current decline
but the historic disappearance of malaria from Europe and North
America too, largely through the shrinking size of households. The
authors concluded that “the probability of malaria
eradication jumps sharply when average household size drops below
four persons”.

The reason for this is that an infected mosquito returns to feed
in roughly the same place night after night and its success rate in
infecting a new human being is too low for the disease to spread if
there are fewer than four people per household. That’s great news,
because household size is falling throughout the world, so even
without intervention malaria should continue to decline. Yet that
study, unlike the altitude one, went largely unreported.

As did the fact that new HIV infections worldwide have fallen by 33 per cent in total, and 52 per
cent in children, since 2001. Aids-related deaths are down by 30
per cent since 2005. New cases of tuberculosis have been falling for a decade too, and mortality from
TB is 45 per cent down since 1990. Again, these are remarkable and
unexpected turn-arounds. Go back to the turn of the century and you
will find public health officials uniformly gloomy about the
prospects for Aids and TB.

In 2000, for example, the US National Intelligence Council predicted that the burden of HIV/Aids and TB
was going to go on getting so much worse for at least ten years
that it “is likely to aggravate and, in some cases, may even
provoke economic decay, social fragmentation and political
destabilisation in the hardest-hit countries in the developing and
former communist worlds”.

Meanwhile two truly horrible diseases are on the brink of
extinction altogether. Last year there were just 406 cases of polio in the world,
mostly in Pakistan, Somalia and Nigeria. Polio’s eradication is
long overdue, but it’s getting closer. There has been an even
faster decline in guinea worm, a painful parasite that you catch
from ingesting water fleas when drinking, and which grows down your
leg and erupts from your foot. The only remedy is to pull it out
inch by inch over months (I do hope you have finished

More than three million people had guinea worm in the late
1980s, when Jimmy Carter made it one of his top priorities. Last
year just 148 of the parasites survived, mostly in South Sudan.
Despite the civil war there, the eradication work by Mr Carter’s
volunteers continues and just three cases have emerged this year. When guinea worm is
gone, because it infects no other species, it will be the first
deliberate extinction of a living species (smallpox is a virus, and
anyway remains in a laboratory). Good riddance.

Not all diseases are retreating. Dengue fever, spread by a
different (day-feeding) genus of mosquito from the (night-feeding)
malarial genus, is getting steadily more common right across the
planet. Antibiotic resistance is complicating the fight against
some bacteria. But overall the tropical world is seeing the same
huge retreat of infectious death that happened in the temperate
world during the previous century.

And nobody seems terribly interested. Why is this? You can
understand why journalists don’t tell good news stories more often;
their motto, after all, is: “If it bleeds, it leads.” You can be
pretty sure that a country that’s gone out of the headlines —
Sierra Leone, for example — is doing pretty well.

But why are public health officials not keener to blow their own
trumpets? It is, after all, the hard work of dedicated
professionals, backed up by millions of volunteers and funded by
generous philanthropists, that is driving these contagions out.

Here’s where I turn a touch cynical. A few years ago, maternal
mortality — that is, death among women giving birth — began to fall
fast, having stagnated for a decade or so. The editor
of The Lancet recounted how he came under co-ordinated and
determined pressure from women’s health advocates to delay
publication of the news of this fall in maternal mortality because,
said those pressurising him, “good news would detract from the
urgency of their cause”. Aha.

By Matt Ridley | Tagged:  rational-optimist  the-times