Identifying a Pathogen

In his awesome book on pathogens that jump species, Spillover, David Quammen has one section on how the process of identifying a pathogen proceeds. He uses the SARS breakout of 2003 as an example. When it went global starting at Hong Kong, he writes nobody knew what caused it, hence the name:

“Ebola is a virus. Hendra is a virus. Nipah is a virus. SARS is a syndrome.”

 

Most tests in medical labs are designed in a particular way:

“Such tests essentially give you a positive, negative, or approximated answer in response to a specific question: Is it this? Finding an entirely new pathogen is more difficult. You can’t detect a microbe by its molecular signature until you know roughly what that signature is.”

So when trying to identify a new pathogen, scientists try growing it in a culture and then peer at it through a microscope. Then they tried peering through an electron microscope, and thus realized it was a coronavirus, i.e., viral particles “encircled by a corona of knobs”.

 

But could you be sure this was the pathogen you were searching for? After all, it might be some other microbe in the body, not the one related to the disease/syndrome you were trying to figure. To establish causality, they took blood serum from SARS patients which would obviously have antibodies. If you let loose the SARS antibodies on the virus-in-the-lab that you thought was the culprit, there would be war. If not, nothing. The result?

“(It) was like splashing holy water at a witch. The antibodies recognized the virus and reacted strongly.”

And thus it was confirmed that the cause of SARS was the, er, SARS coronavirus, abbreviated to SARS-CoV.

Comments

Post a Comment

Popular posts from this blog

Student of the Year

Image
As a toddler, my daughter loved Alia Bhatt’s songs, esp. the ones from Student of the Year . (That movie did have many good songs and well-choreographed dances). Fast forward to present day, when she is 12 yo. She rarely watches Hindi movies now, but one of the few ones she likes of late, Raja aur Rani ki Prem Kahani has, yes, Alia Bhatt.   If I had any hopes that there was anything to be read in the name of her toddler-time favorite ( Student of the Year ), they have been dashed. Our conversations come exam time are perfectly captured by this photo and its caption: In fact, the pic below captures how she and I look at her answer sheets – me intently, she with an expression of “It’s over, so why are you even looking at it?”   Of late, we pull her leg and tell her that she isn’t showing any signs of academic prowess, she’d better find a rich guy to marry. Some time later, she showed us this meme on the Internet: “Me No Study, Me No Care Me Go Marry Millionaire If He Die
Read more

Animal Senses #7: Touch and Remote Touch

Instinctively, we think touch is based on contact. Not entirely true, explains Ed Yong in Immense World – there’s a more important aspect than contact: “These incredible feats are possible through movement. If you rest a fingertip upon a surface, you can get only a limited idea of its features. But as soon you’re allowed to move, everything changes. Hardness becomes apparent with a press. Textures resolve at a stroke.” As you run your fingers over a surface, they hit the tiny peaks and troughs and set off vibrations in the mechanoreceptors at their tips.   At the tip of its snout, the star-nosed mole has many pairs of hairless appendages. It uses them to touch things around itself. Alive or dead? Food or ignore? It does these movements at an insane speed. In the time it takes to blink our eyes, the star-nosed mole can probe, identify and swallow its food. “Light may be the fastest thing in the universe, but light sensors have their limits, and the star-nosed mole’s sense of
Read more

The Retort of the "Luxury Person"

Image
Coming up with biting and witty retorts. It’s something we dream of, but rarely manage to pull off. Worse, the more we stew over the offending remark, the more likely we are to come up with that dream retort, as Calvin ruefully points out: During our last holiday at the Taj Resort, seeing my wife carrying towels to our poolside chairs, one of the kids there mistook her for a member of the staff and asked for a towel. When my wife narrated this to us, I did not imagine that my 8 yo daughter would come up with her own retort. But a day later, my daughter recapped the incident, an incident that didn’t even involve her in the first place , and said, “You know what I’d have told that kid who asked for the towel?”. And without waiting for an answer, she told us anyway: “I don’t work here. I too am a luxury person who is living at this resort. Go get your own towel.” We were highly amused by the phrase she had coined: “luxury person”. It certainly captures the kind of holid
Read more