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Hunting Down a Killer
By Jacqueline Adams
Can virus hunters track—and stop—the deadly bird flu virus before it spreads out of control?
In 1997, three-year-old Lam Hoi-ka was admitted to a hospital in Hong Kong. At first, the boy seemed to be suffering
from a typical flu virus. His throat was sore and he had a stomachache and a fever. Then, deadly symptoms appeared.
The boy began to have difficulty breathing. That caused his lungs, liver, and kidneys to fail. Within a week, he was dead.
Lam Hoi-ka's death baffled his doctors. Tissue samples from the boy's throat tested positive for flu—but not for the types
of flu known to make humans sick. What kind of flu virus had taken the life of this otherwise-healthy young child? Were
other people at risk of contracting it?
To get to the bottom of the mystery, doctors in Hong Kong needed help. They sent tissue samples to top labs around the
world. Soon, news came from Holland. A team of Dutch scientists had made a terrifying discovery. Lam Hoi-ka had died
from a lethal strain of flu previously found only in birds. Somehow, the virus had made the leap from birds to humans.
The new killer, soon to be known as "bird flu," triggered fear around the world. Scientists worried that the virus could
cause a pandemic.
Fortunately, the virus did not travel outside Hong Kong—at least, not in 1997. But scientists and health officials worry
that it's only a matter of time before bird flu or another new flu virus spreads out of control. In a race against time, they're
working on solutions to protect the world from a deadly outbreak.
For the Birds
Most people call the new disease "bird flu" or "avian influenza." But scientists call it H5N1. The letters and numbers
stand for the types of proteins on the surface of a particular flu virus.
The virus that causes bird flu started in wild waterbirds, such as ducks, geese, and swans. In fact, H5N1 has been
circulating among these birds for a long time. Their bodies have adapted to it, so it does not kill them or make them sick.
But sometimes, infected waterbirds mingle with chickens and other domestic poultry that have not adapted to the virus.
When chickens come into contact with the waterbirds' waste and saliva, they too become infected with H5N1. The virus
then spreads out of control throughout the chickens' bodies and kills them.
The Virus Leaps to Humans
Domestic poultry on the island of Hong Kong came down with H5N1 in 1997—just two months before Lam Hoi-ka's
death. Witnesses reported seeing chickens shaking, with saliva coming out of their mouths. They claimed that some
chickens had laid "eggs without shells." Scientists who studied the birds noted that the virus was extremely infectious—
in chickens. But at that point, experts saw no need for alarm where humans were concerned. The virus appeared to be
confined to the bird population.
Then the virus did something it had never done before: it spread from birds to humans. Lam Hoi-ka was the first victim.
He had likely contracted the disease from baby birds that his preschool kept as pets.
Soon afterwards, eighteen more humans caught the virus, and six died. Like Lam Hoi-ka, all of these victims had come
into contact with domestic poultry shortly before their deaths. They had either bought poultry or shopped near places
that sold chickens. To prevent bird flu from spreading, officials destroyed all the poultry on the island of Hong Kong—a
total of one and a half million birds. For a while, it seemed that they had succeeded in wiping out bird flu.
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Then, in 2003, the virus again jumped from poultry to humans—and began to spread. Over the next four years, almost
three hundred people were infected in a dozen Asian and African countries. Nearly two-thirds of the victims died.
How does this virus kill? First, it enters the lungs, where it attaches to cells, which are the body's most basic units of life.
Then, the virus quickly multiplies. Victims develop a high fever, vomiting, and diarrhea. Soon, their lungs fill with fluid and
can no longer deliver the oxygen their bodies need. As a result, the victims die.
No Ordinary Flu
Other flu viruses circulate among humans without causing much harm. Humans have been exposed to common flu
viruses for years, so the body's system of defense—the immune system—has learned to resist them. Ordinary flu
viruses are sometimes deadly to the elderly, the very young, or those with weakened immune systems. But most
infected people—a far greater percentage than the one-third who survived the 2003 bird flu outbreak—are back on their
feet after just a few days or weeks. So, what makes bird flu so lethal? H5N1 is new to humans, so it catches the immune
system off guard.
"Our immune system is not used to H5N1. So there's little to no immunity in humans," explains John El-Attrache, an
avian flu scientist at Texas A&M University. That's why H5N1 can infect and kill even young, healthy adults. As ElAttrache explains, "This virus has no boundaries with the type of people it infects."
Recipe for a Pandemic
H5N1 is already lethal. It will become a true nightmare under three conditions: 1. It must be a new virus to which
humans have little or no immunity. Check. 2. It must be able to multiply in the human body and cause serious illness.
Check. 3. It must spread easily from human to human.
The bird flu virus meets the first two conditions. But so far, H5N1 has proved difficult for humans to catch from other
humans. Most bird-flu victims contracted the virus only after direct contact with infected poultry. Victims included workers
who slaughtered and plucked chickens and children, like Lam Hoi-ka, who played in areas littered with waste from
infected birds. El-Attrache says that even the passing of the virus "from birds to humans is still very rare, and it requires
[a great deal of] contact."
A few victims reported catching the virus from an infected family member. But the flu stopped spreading after passing
from one person to just one other person. Why? Maybe it's because H5N1 multiplies deep in the lungs—not in the nose
and throat, where it could be spread by sneezing and coughing. While that's good news, scientists are still racing
urgently to stop H5N1. Sometimes, viruses suddenly develop the ability to spread like wildfire. That could happen with
H5N1.
Mutant Viruses
How can a virus start spreading more easily than it did at first? One reason involves the way viruses multiply. A virus
invades healthy cells and forces them to make copies of it. Sometimes, when the copies are made, mistakes—called
mutations—occur. If the right set of mutations happens, H5N1's behavior could change, making the virus more
dangerous to humans.
The right series of mutations could allow H5N1 to attach to cells in the human nose and throat. Then humans could
transmit the virus by coughing and sneezing. Bird flu might spread as easily as the common cold.
How likely is it that mutations will occur when H5N1 multiplies? Very likely, according to Terrence Tumpey, a senior
microbiologist at the Centers for Disease Control and Prevention (CDC). "We consider it a very sloppy virus in terms of
how it replicates itself," Tumpey explains. "It's always making mistakes."
A Deadly Mix
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Here's another way that H5N1 could become more dangerous. Sometimes, two different flu viruses invade the same
human cell. Then, material from the two viruses can merge and form a new virus. As Joseph Bresee, head of
epidemiology at the CDC, explains, "The new virus would share a mixture of genes [from the two original viruses]."
Suppose one of the original viruses is a common flu virus and the other is H5N1. This could spell disaster.
Why? The genes are the parts of a virus that tell it how to behave. In a highly contagious virus like a common flu, a gene
contains information about how to spread. In lethal H5N1, a gene contains information about how to cause deadly
symptoms. If the viruses mix, and the new virus gets both genes, we then would have a deadly new virus that spreads
easily among humans!
Heading Off Disaster
How can scientists and health officials protect humans from H5N1? The first line of defense is to stamp out the virus as
soon as it shows up in domestic birds. Health officials are on the alert for reports of infected poultry. They act swiftly to
have the poultry destroyed before it can spread the virus to humans. Officials are also developing strategies to keep
healthy poultry from mingling with wild waterbirds, which might be carrying H5N1. This is especially important in areas
where many people keep open-air, backyard poultry flocks.
Keeping Safe
To further prevent the spread of disease, many health officials suggest avoiding crowds—especially crowds of children.
According to the World Health Organization, children are the main transmitters of viruses like the common flu. A study
performed at Children's Hospital in Boston showed that preschoolers in particular are prone to spreading infection. Not
only are they more likely to pick their noses and not cover their sneezes and coughs, preschoolers can spread a virus
for up to a week before showing symptoms.
Yet, avoiding children—and crowds in general—isn't practical for most people. Further, even someone who avoids
crowds might unknowingly touch a doorknob or other surface that an infected person has touched. Under the right
conditions, H5N1 can survive for days on such a surface.
Luckily, the virus can't enter the body through the skin. It usually gets in through the eyes, nose, or mouth. So, health
officials urge people not to touch these areas of their bodies without first washing or sanitizing their hands.
Developing New Weapons
Many scientists believe that even if people take all possible precautions, it's only a matter of time before a virus such as
H5N1 triggers a pandemic. So, scientists are preparing for battle by developing new drugs and vaccines.
Doctors already give their patients shots called vaccines to protect patients against common flu viruses. A vaccine is a
medicine that contains a safe, inactive form of a virus. The inactive virus cannot multiply. When doctors inject it into a
patient, the patient's immune system develops antibodies, or proteins that are tailor-made to fight the virus. The patient's
immune system then becomes ready to strike down the active virus if it ever tries to invade.
Scientists have recently developed a vaccine that protects against H5N1. At least, the vaccine protects against the
current strain of H5N1. But scientists worry what will happen to H5N1 if it mutates. The current vaccine would not
necessarily be effective against a mutation of H5N1, so the vaccine might not be useful in battling a pandemic.
Currently, creating vaccines that target new or mutated flu viruses can take months. Scientists are searching for ways to
speed up the process, so they can rush into action if a lethal new flu virus starts to spread.
Looking to the Past
Scientists were sure that studying a flu virus that had caused a past pandemic would offer insight into how such viruses
behave and what makes them so lethal. It might also help scientists to develop drugs and vaccines to conquer such
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viruses.
First, they had to find a virus to study. That was easier said than done. No past pandemic virus remained active in the
present. Scientists would have to bring one back from the dead. Could they do it? Should they?
Digging Up the Dead
In 1997, Jeffery Taubenberger, a scientist at the Armed Forces Institute of Pathology (AFIP) in Maryland, decided to go
for it. He planned to bring back Spanish influenza—a deadly flu virus that killed up to 50 million people worldwide in
1918.
A doctor told Taubenberger about a small town in Alaska whose population had been almost wiped out by the 1918 flu.
Seventy-two victims had been buried in a mass grave. The frozen ground had most likely preserved their body tissues
without damaging the virus's genetic material.
The doctor obtained permission from the town council to dig up the grave and collect tissue samples. He sent the
samples to Taubenberger.
A Killer Returns
Now, the scientists had to learn exactly how the virus creates itself inside a cell. To learn that information,
Taubenberger's team worked hard studying the virus's genetic material. Finally, in 2005 they succeeded in uncovering
the blueprint for building the 1918 virus.
Using what they had learned, scientists produced the virus's genes. They sent the genes to Terrence Tumpey at the
CDC. Tumpey injected the genes into a cell, and the genes directed the cell to start constructing virus proteins. Tumpey
said, "Once the virus proteins are all made inside the cell, then the virus assembles itself." The 1918 virus was back.
What might scientists learn from it?
Help from a Killer Virus
To insure that the killer virus won't escape the confines of the lab—and possibly kill again—it is held under strict security.
To enter the lab, Tumpey has to pass through many security systems, including ones that use a fingerprint scanner and
an iris scanner. He breathes through a respirator when handling the virus, and he has to shower before leaving the
building.
By conducting animal experiments with the 1918 virus, Tumpey has already identified some of the proteins that made
the virus so lethal and allowed it to spread so easily. Scientists are now working to develop antiviral drugs that will attack
those proteins.
The resurrected killer may also help identify effective vaccines. Tumpey said, "We are using it to test whether or not a
particular vaccine can protect against this pandemic virus. If it can, then we think it would protect against future
pandemic viruses."
Ironically, a virus that once killed millions might someday help save millions of lives. Scientists have a long way to go
before this becomes a reality, but they are determined to win the race against time.
SIDEBAR: Far from a First
Bird flu isn't the first disease to jump from other animals to humans. In fact, experts believe that most infectious diseases
that afflict humans came from our feathered and four-footed friends. The famous bubonic plague, or "Black Death,"
which killed one-third of Europe's population in the 14th century, was spread by rats and fleas.
Other disease-transmitting animals include goats—thought to have spread tuberculosis (TB) to humans—and pigs,
which are believed to be the original carriers of whooping cough. Once TB and whooping cough spread to humans, the
bacteria that cause those diseases mutated. The mutations allowed the diseases to spread easily from human to
human.
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Scientists think cows were probably the source of the viruses that mutated to cause measles and smallpox in humans.
But cows also helped bring vaccines to the world. In 1796, an English doctor discovered that patients who had
recovered from a cattle disease called cowpox were immune to the more dangerous smallpox. People then began to
"vaccinate" themselves by catching cowpox on purpose.
SIDEBAR: Protecting Yourself from Bird Flu
At present, the chance that you will catch bird flu is very small. If the virus is not properly controlled, however, someday
it might spread easily among humans. Start now to protect yourself and your family. Here are some tips:
Cover your mouth and nose when you cough or sneeze.
Wash your hands regularly.
Regularly clean surfaces such as tabletops and kitchen counters with disinfectants.
Avoid unnecessary contact with live and dead birds.
If you cook poultry or eggs, make sure to cook the food thoroughly.
When preparing raw poultry for cooking, keep it separate from cooked or ready-to-eat foods.
"Hunting Down a Killer" by Jacqueline Adams from Expert 21 21Book, Course II, Volume 2. Copyright © 2010 by
Scholastic Inc. Published by Scholastic Inc.
™ & © 2020 Scholastic Inc. All rights reserved.
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