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HEALTH: Climate Change Brings New Diseases
By Julio Godoy
BERLIN, Jun 19 (IPS) - As its name suggests, the West Nile virus, a leading cause of a form of
meningitis and a neuro-invasive disease, has until recently been reported
mostly in tropical and sub-tropical African regions. But it is now about to
become a global virus.
"Due to climate change, regions with moderate temperatures, that is most of
Europe and North America, are now facing diseases that were thought
completely exotic in these areas," says Thomas Mettenleiter, president of the
German Federal Research Institute for Animal Health, also known as the Friedrich-
Loefller Institute (FLI), based in the Riems, a Baltic Sea island 200 km
north of Berlin.
About 100 health experts who gathered at Riems last month for a conference
on health challenges posed by climate change and globalisation agreed that
the spread of disease was no longer only through air and sea travel. The
acceleration of climate change has created conditions for these vectors,
mostly mosquitoes, but also rodents and other species, to settle in habitats
formerly inappropriate for them.
"Since the end of the last great ice age some 10,000 years ago, the average
European temperature has risen by six degrees Celsius," says Horst Aspoeck,
head of the department of medical parasitology at the University of Vienna.
This regional warming accelerated sharply after industrialisation began some
200 years ago, Aspoeck said. "For this century, we have to fear a new, rapid
temperature jump of at least three degrees Celsius in Europe."
"In recent months, numerous cases of WNV (West Nile Virus) infections have
been reported in Austria, Hungary, and Bulgaria," said Mettenleiter from the
FLI. "For Germany, this means that the West Nile Virus is already at our
doorsteps."
The virus has been reported already in the United States. A total of 3,630
cases of WNV neuro-invasive disease (WNND), including 124 deaths, were
reported in the country in 2007, according to the
U.S. Federal Centre for Disease Control and Prevention. The disease was
first identified in New York in 1999, and has now spread across the country
to reach California.
Virologists expect a similar spread of the yellow fever mosquito, which can
transmit diseases such as dengue, chikungunya, and yellow fever. "It is only a
matter of time before the yellow fever mosquito becomes domestic in Spain,
and with it maybe dengue and yellow fever," says Matthias Niedrig, a
virologist at the German Robert-Koch-Institute for health research.
Lyle Petersen, director of the U.S. division of vector-borne infectious diseases
at the National Centre for Zoonotic, Vector-Borne and Enteric Diseases, and
who in 2003 contracted the WNV, observed the virus's transmission speed
under different temperatures.
Under average temperatures of 17 degrees Celsius, it took 30 days before the
infected mosquito transmitted the virus. By the end of the period, most of the
mosquitoes observed had died - it was too cold for them to survive. But if
the average temperature was 30 degrees Celsius, it took only five days for
the transmission because thanks to the warm temperatures, most mosquitoes
survived.
In some cases, however, apparently negligible temperature changes suffice to
spark a pandemic. In 1997, an observed rise of 0.5 degrees Celsius in the
surface of the Indian Ocean waters provoked a massive outbreak of the
Rift-Valley fever in East Africa. The warmer waters provoked heavy
rains, and the high temperatures, the humidity and inadequate rainwater
drainage created the perfect incubation conditions for mosquitoes
transmitting the virus.
The virus first killed hundreds of thousands of goats and sheep in Kenya,
Somalia and Tanzania, provoking a famine in the region - without goats and
sheep, the peasant population had less to eat. But then, humans contracted
the virus. According to the World Health Organisation, several hundreds died
of diseases caused by the virus in the three countries.
The Rift-Valley virus case in Eastern Africa shows how climate change is
threatening public health in developing countries. Compounded with rapid,
uncontrolled urbanisation and insufficient public hygiene, climate change is
creating conditions for the return, or the worsening, of diseases thought to
be under control, according to a report by the
University College London (UCL) and the medical journal The Lancet.
The report, titled 'Managing the health effects of climate change', says that
climate change is now the biggest health threat globally, especially in
developing countries. "The epidemiological outcome of climate change on
disease patterns worldwide will be profound, especially in developing
countries where existing vulnerabilities to poor health remain."
The report says the urban population in developing countries is projected to
increase from 2.3 billion in 2005 to 4 billion by 2030, and this will be
accompanied by an expanding urban sprawl and poor housing. "This change
will inevitably increase the risk of heat waves and heat strokes in cities in
developing countries as a result of the so-called heat island effect."
The heat island effect refers to the significantly higher temperatures observed
in metropolitan areas, compared with their surrounding rural areas, and
caused by the modification of landscape and by waste heat generated by the
massive use of energy in the cities.
The report's lead author, Anthony Costello of the UCL, told IPS that "the
failure to act (to stop climate change) will result in inter-generational
injustice, with our children and grandchildren scorning our generation for
ignoring the climate change threat - with similar moral outrage to how we
today look back on those who brought in and did nothing to stop slavery."
(END/2009)
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