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HANOI, LUANDA––If an epidemiologist’s worst nightmare isn’t
the avian influenza strain called H5N1, it might be Marburg hemorrhagic
fever, a virulent close cousin to the better known Ebola virus. Both are
zoonotic diseases, meaning that they spread to humans from animals. With
a quirk or two of virus evolution, both could depopulate continents. The
worst-ever outbreaks of each are raging right now in Southeast Asia and
Central Africa.
H5N1, discovered after it killed three people in Hong Kong in 1997, apparently
crossed from migratory wild birds to ducks and geese reared in huge outdoor
pens and paddies in southern China, crossed to indoor-raised chickens,
then raced throughout Southeast Asia with the mostly illegal but lightly
prosecuted commerce in gamecocks.
Killing about 70% of the humans who contract it from birds, H5N1 has not
killed millions chiefly because it has not evolved into a form that spreads
easily from human to human, and does not spread easily from bird to human.
Only the estimated 25 to 40 million Southeast Asians who raise poultry
are believed to be at risk of becoming infected by the bird-to-human route.
A 10-year-old girl who died on March 27, 2005 in Hanoi was the 50th known
human fatality since January 2004, and the 36th Vietnamese. Twelve Thais
have died, and two Cambodians. There have been more than 3,000 known outbreaks
among poultry. More than 60 million birds have either died from H5N1 or
have been gassed, buried alive, or even burned alive in mostly futile
control efforts.
China introduced an H5N1 vaccine for poultry in December 2003, has since
introduced two more of increasing efficacy, and has innoculated more than
2.7 billion domestic fowl since January 2004. Indonesia began vaccinating
50 million poultry in March 2005. There are H5N1 vaccines for humans,
too, but world production of all human flu vaccines combined is only 500
million doses per year. Only the U.S. is believed to have vaccination
coverage enough to slow a serious flu epidemic.
Marburg was first identified in 1967, after laboratory workers in Marburg
and Frankfort, Germany, and Belgrade, Yugoslavia, received infected monkeys
who were captured in Uganda. Until 2005 the biggest known outbreak killed
123 people from 1998 to 2000 in the Democratic Republic of Congo. As with
Ebola, the first victims are typically young men who have eaten monkeys.
They infect their families, who infect health workers.
Like Ebola, Marburg is so infectious and kills so quickly that it has
so far always burned itself out before mutating into a strain that victims
could carry into contact with many others. Ebola victims typically have
contact with 12 other people before death; Marburg victims have contact
with just four.
The current outbreak hit Uige, Angola, 200 miles north of Luanda, in October
2004. Government censorship suppressed awareness of it until it reached
the outskirts of Luanda, killing 29 people in the first four days of April
2005. People believed to have had exposure to victims were quarantined
as far away as Italy and Portugal. The known death toll by April 5 was
156, including more than 125 children under age 15, with 88% mortality
among identified cases. While the initial source of the outbreak is unknown,
recycling the needles used to give childhood vaccinations is believed
to be the major cause of the unprecedentedly high mortality among children.
