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While everyone was talking about the swine flu, researchers at the University of North Carolina have found the reason why its far-scarier cousins, the avian flu strains, didn’t become a full-blown pandemic. Turns out, we have our cold noses to thank:
All and all, 248 humans have died from the H5N1 according to WHO data as of January 2009. H5N1, as a strain, infects more species than any previously known flu virus, is deadlier than previous strains, and continues to evolve becoming both more widespread and more deadly. But even still, fears of a pandemic have yet to be realized. Now, researchers might have found the reason: our noses are too cold for the Avian flu. [...]
The difference in temperature, internally, between a human and a bird isn’t all that different – people maintain an internal temperature of about 37 degrees celcius, whereas birds stay a little warmer, around 40 degrees celcius. Researchers from the University of North Carolina wanted to know how these temperature differences might affect avian influenza viruses. They took a avian virus strain, H4N6, and human flu H3N2, and tried to infect human airway epithelial cells – the cells that line our noses and lungs. Both, they found, could infect and replicate quite quickly human airway epthelial cells at 37 degrees celcius, though the avian ones were a little slower in general than the human ones. But when the temperature was dropped to that of our noses – a bit cooler 32 degrees celcius – the avian virus replication slowed to a snail’s pace, 3-5 log units below the human virus’ speed. They tried a different avian strain – H5N3 – and found the same results. So they tried the deadly virus itself, H5N1 isolated from a dead person, and even it fared poorly. It seems that something about avian flu viruses simply can’t function right in cooler temperatures.
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If you’ve been watching all of the media hype, you’d be forgiven if you think that the swine flu pandemic will kill us all. But according to some scientists, it’s actually much milder than your average run-of-the-mill flu that hit every winter:
The swine virus does appear able to spread easily among humans, which persuaded the WHO to boost its influenza pandemic alert level to phase 5, indicating that a worldwide outbreak of infection is very likely. And the CDC reported on its website that "a pattern of more severe illness associated with the virus may be emerging in the United States." [...]
But certainly nothing that would dwarf a typical flu season. In the U.S., between 5% and 20% of the population becomes ill and 36,000 people die — a mortality rate of between 0.24% and 0.96%.
Dirk Brockmann, a professor of engineering and applied mathematics at Northwestern University in Evanston, Ill., used a computer model of human travel patterns to predict how this swine flu virus would spread in the worst-case scenario, in which nothing is done to contain the disease.
After four weeks, almost 1,700 people in the U.S. would have symptoms, including 198 in Los Angeles, according to his model. That’s just a fraction of the county’s thousands of yearly flu victims.
Karen Kaplan and Alan Zarembo of The Los Angeles Times has more: Link
The outbreak of swine flu, first in Mexico then cases all over the world, has gotten a lot of people worried. And for a very good reason: despite the existence of scarier diseases caused by exotic viruses like Hantavirus and Ebola, influenza still reigns as the number one infectious killer in modern times.
Unlike regular seasonal epidemics of the flu, there are also rare but deadly pandemics, i.e. cases of influenza that spread on a worldwide scale and infect a large proportion of the human population.
While it's important not to panic (the swine flu appears to be highly treatable with conventional antiviral drugs), a review of past pandemics will elucidate why authorities are responding quickly to this outbreak. Here's a quick summary of the 5 deadliest pandemics in history:
The
very first pandemic in recorded history was described by Thucydides. In
430 BC, during the Peloponnesian war between Athens and Sparta, the Greek
historian told of a great pestilence that wiped out over 30,000 of the
citizens of Athens (roughly one to two thirds of all Athenians died).
Thucydides described the disease as such "People in good health were all of a sudden attacked by violent heats in the head, and redness and inflammation in the eyes, the inward parts, such as the throat or tongue, becoming bloody and emitting an unnatural and fetid breath." Next came coughing, diarrhea, spasms, and skin ulcers. A handful survived, but often without their fingers, sights, and even genitals (Source)
Until today, the disease that decimated ancient Athens has yet to be identified.
In 165 AD, Greek physician Galen described an ancient pandemic, now thought to be smallpox, that was brought to Rome by soldiers returning from Mesopotamia. The disease was named after Marcus Aurelius Antoninus, one of two Roman emperors who died from it.
At its height, the disease killed some 5,000 people a day in Rome. By the time the disease ran its course some 15 years later, a total of 5 million people were dead.
In
541-542 AD, there was an outbreak of a deadly disease in the Byzantine
Empire. At the height of the infection, the disease, named the Plague
of Justinian after the reigning emperor Justinian I, killed 10,000 people
in Constantinople every day. With no room nor time to bury them, bodies
were left stacked in the open.
By the end of the outbreak, nearly half of the inhabitants of the city were dead. Historians believe that this outbreak decimated up to a quarter of human population in the eastern Mediterranean. (source)
What was the culprit? It was the bubonic plague, caused by the bacterium Yersinia pestis. This outbreak, the first known bubonic plague pandemic in recorded human history, marked the first of many outbreaks of plague - a disease that claimed as many as 200 million lives throughout history.
After the Plague of Justinian, there were many sporadic oubreaks of the plague, but none as severe as the Black Death of the 14th century.
While no one knows for certain where the disease came from (it was thought that merchants and soldiers carried it over caravan trading routes), the Black Death took a heavy toll on Europe. The fatality was recorded at over 25 million people or one-fourth of the entire population. (source)
It's interesting to note that the Black Death actually came in three forms: the bubonic, pneumonic, and septicemic plague. The first, the bubonic plague, was the most common: people with this disease have buboes or enlarged lymphatic glands that turn black (caused by decaying of the skin while the person is still alive). Without treatment, bubonic plague kills about half of those infected within 3 to 7 days.
In
pneumonic plague, droplets of aerosolized Y. pestis bacteria
are transmitted from human to human by coughing. Unless treated with antibiotics
in the first 24 hours, almost 100% of people with this form of infection
die in 2 to 4 days.
The last form, septicemic plague, happens when the bacteria enter the blood from the lymphatic or respiratory system. Patients with septicemic plague develop gangrenes in their fingers and toes, which turn the skin black (which gives the disease its moniker) Though rare, this form of the disease is almost always fatal - often killing its victims the same day the symptoms appear. (Photo and Source: Insecta-Inspecta)
We haven't heard the last of the bubonic plague. In 1855, another bubonic plague epidemic (named the Third Epidemic) hit the world - this time, the initial outbreak was in Yunnan Province, China. Human migration, trade and wars helped the disease spread from China to India, Africa, and the Americas.
All in all, this pandemic lasted about 100 years (it officially ended in 1959) and claimed over 12 million people in India and China alone.
Emergency military hospital at Camp Funston, Kansas (Image: National Museum
of Health and Medicine, Armed Forces Institute of Pathology, Washington
D.C.) via PLoS
Biology
In
March 1918, in the last months of World War I, an unusually virulent and
deadly flu virus was identified in a US military camp in Kansas. Just
6 months later, the flu had become a worldwide pandemic in all continents.
When the Spanish Flu pandemic was over, about 1 billion people or half the world's population had contracted it. It is perhaps the most lethal pandemic in the history of humankind: between 20 and 100 million people were killed, more the number killed in the war itself (Source)
The Spanish Flu actually didn't originate in Spain - it got its name because at the time, Spain wasn't involved in the war and had not imposed wartime censorship, thus it received great press attention there.
Recently, scientists were able to "resurrect" the virus from a well-preserved corpse buried in the permafrost of Alaska.
