Carl Zimmer

A Planet of Viruses

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eadyidihhas quoted3 years ago
“Viruses are not living organisms,”
b3467991634has quoted3 months ago
Viruses wreak chaos on human welfare, affecting the lives of almost a billion people. They have also played major roles in the remarkable biological advances of the past centur
Nicolas Palacioshas quotedlast year
Viruses are indeed exquisitely deadly, but they have provided the world with some of its most important innovations. Creation and destruction join together once more.
Nicolas Palacioshas quotedlast year
Many scientists now argue that viruses contain a genetic archive that’s been circulating the planet for billions of years. When they try to trace the common ancestry of virus genes, they often work their way back to a time before the common ancestor of all cell-based life
Nicolas Palacioshas quotedlast year
When mimiviruses invade amoebae, they don’t dissolve into a cloud of molecules. Instead, they set up a massive, intricate structure called a viral factory. The virus factory takes in raw ingredients through one portal, and then spits out new DNA and proteins through two others. The viral factory looks and acts remarkably like a cell. It’s so much like a cell, in fact, that La Scola and his colleagues discovered in 2008 that it can be infected by a virus of its own. It was the first time anyone had found a virus of a virus. It was yet another thing that ought not to exis
Nicolas Palacioshas quotedlast year
Forced to carry tiny genomes, viruses could not make room for genes that did anything beyond make new viruses and help those viruses escape destruction. They could carry genes to let them eat, for example. They could not turn raw ingredients into new genes and proteins on their own. They could not grow. They could not expel waste. They could not defend against hot and cold. They could not reproduce by splitting in two. All those nots added up to one great, devastating Not. Viruses were not alive
Nicolas Palacioshas quotedlast year
In the late 1700s, the British physician Edward Jenner invented a safer smallpox vaccine based on stories he heard about how milkmaids never got smallpox. Cows can get infected with cowpox, a close relative of smallpox, and so Jenner wondered if it provided some protection. He took pus from the hand of a milkmaid named Sarah Nelmes and inoculated it into the arm of a boy. The boy developed a few small pustules, but otherwise he suffered no symptoms. Six weeks later, Jenner variolated the boy—in other words, he exposed the boy to smallpox, rather than cowpox. The boy developed no pustules at all. Jenner published a pamphlet in 1798 documenting this new, safer way to prevent smallpox. He dubbed it “vaccination,” after the Latin name of cowpox, Variolae vaccinae.
Nicolas Palacioshas quotedlast year
The first effective way to prevent the spread of smallpox probably arose in China around AD 900. A physician would rub a scab from a smallpox victim into a scratch in the skin of a healthy person. (Sometimes they administered it as an inhaled powder instead.) Variolation, as this p
Nicolas Palacioshas quotedlast year
Variolation, as this process came to be called, typically caused just a single pustule to form on the inoculated arm.
Nicolas Palacioshas quotedlast year
Ebola, for example, is a horrific virus that can cause people to bleed from all their orifices, including their eyes. It can sweep from victim to victim, killing almost all its hosts along the way. And yet a typical Ebola outbreak only kills a few dozen people before coming to a halt. The virus is just too good at making people sick, and so it kills its victims faster than it can find new ones.
Nicolas Palacioshas quotedlast year
HIV, scientists found, belongs to a large group of slow-growing retroviruses, known as lentiviruses.
Nicolas Palacioshas quotedlast year
Retroviruses insert their genetic material into their host cell’s DNA. When the host cell divides, it copies the virus’s DNA along with its own. Under the certain conditions, the cell is forced to produce new viruses—complete with genes and a protein shell—which can then escape to infect a new cell. Retroviruses sometimes trigger cells to turn cancerous if their genetic material is accidentally inserted in the wrong place in their host’s genome. Retroviruses have genetic “on switches” that prompt their host cell to make proteins out of nearby genes. Sometimes their switches turn on host genes that ought to be kept shut off, and cancer can result.
Nicolas Palacioshas quotedlast year
Thanks to gene borrowing, viruses may also be directly responsible for a lot of the world’s oxygen
Nicolas Palacioshas quotedlast year
Cholera, for example, is caused by blooms of waterborne bacteria called Vibrio. But Vibrio are host to a number of phages. When the population of Vibrio explodes and causes a cholera epidemic, the phages multiply. The virus population rises so quickly that it kills Vibrio faster than the microbes can reproduce. The bacterial boom subsides, and the cholera epidemic fades away.
Nicolas Palacioshas quotedlast year
It is hard to find a point of comparison to make sense of such a huge number. Viruses outnumber all other residents of the ocean by about fifteen to one. If you put all the viruses of the oceans on a scale, they would equal the weight of seventy-five million blue whales. And if you lined up all the viruses in the ocean end to end, they would stretch out past the nearest sixty galaxies.
Nicolas Palacioshas quotedlast year
These spots, Herelle concluded, were bacteria battlegrounds in which viruses were killing Shigella and leaving behind their translucent corpses.
Nicolas Palacioshas quotedlast year
Many other viruses, such as rhinoviruses and influenza viruses, reproduce violently. They make new viruses as fast as possible, until the host cell brims with viral offspring. Ultimately, the cell rips open and dies. HPV uses a radically different strategy. Instead of killing its host cell, it causes the cell to make more copies of itself. The more host cells there are, the more viruses there are
Nicolas Palacioshas quotedlast year
This mixing, known as reassortment, is a viral version of sex
Nicolas Palacioshas quotedlast year
Another popular treatment for the cold is antibiotics, despite the fact that they only work on bacteria and are useless again viruses.
Nicolas Palacioshas quotedlast year
The very word virus began as a contradiction. We inherited the word from the Roman Empire, where it meant, at once, the venom of a snake or the semen of a man. Creation and destruction in one word
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