I put on my glasses. What the hell was I looking at on my phone?

From out of the gloom a little face suddenly appeared, looking miserable.

My baby granddaughter, 11 months, had a cold.

The previous day we'd spent hours together crawling around the house, pulling things out of cupboards, hunting down the pets, eating, going to the library and every so often, when she was distracted, I would make a swipe at the dripping tap that was her nose, much to her disgust.

Her dad, my youngest son, sent through film 24 hours later to show the cold had set in, the nose was now running rather than dripping, and her coughing was raspy, lengthy and sometimes ended in tears, ensuring more nose-running, coughing, tears etc.

No temperature though, and she devoured her favourite foods with a relish not seen since her father embraced a barbecued chicken we'd bought him to mark a birthday while he was still in primary school.

I sent through a sympathetic message. Her sleep had been choppy. Her parents slept fitfully because of it.

A day or so later I woke up with a painful throat, raspy cough, headache, blocked nose and the general aches and pains you feel when a cold hits.

By the afternoon my voice had almost gone and I gave up trying to be a normal human being and retreated to bed.

There was another film sent through that night, as I worked my way through a box of tissues and hacked like a wharfie after a lifetime three-packs-a-day habit, of a bouncing granddaughter who'd apparently kicked over her cold.

Her immune system had done its job. The cold virus attacked, the baby's body marshalled all the armory available to fight off an invader and she came out fitter and stronger to fight another virus another day.

But around her there was carnage.

"My head feels like it's full of bricks, but it also feels like it's made of custard at the same time," I wrote to one son when he sent a message to say he wouldn't be at another son's cafe at 5am the next day because he was coming down with something.

"Did you see the baby this week?" I asked.

"Yep," he said.

"She's ground zero."

Around her adults fell like flies.

I was the first, no doubt a combination of age and direct contact for a few hours with the highly mobilised contents of a baby's nostrils.

Her parents went next. My youngest son could count on one hand the number of sick days he's had in more than a decade of working. But his daughter took him down.

My daughter-in-law is also the kind of person who has to be forced to take time off work if she's sick. But the baby's cold felled her.

My former husband lasted 24 hours longer than the rest of us, but retreated when the cold kick-started his sinuses. My two other sons and their partners spent a day laughing at the fact my voice was reduced to a whisper, then they croaked apologies via text messages.

We all spent time with the baby on that fateful day as she crawled and climbed and charmed so that we were blinded to what an efficient little germ-carrying vessel she had become.

She bounced back within 48 hours. Two weeks later my voice is still somewhere between a Mafia Don's and a grandma doing the weekend shift on a 1800-porn line. All of the adults are still hacking, sniffing and complaining of occasional chills and lightheadedness.

Her little immune system is being strengthened with every cold and bug but I'm starting to wonder whether I'll survive, particularly now that grandchild number two is due in early November and number three by mid-January.

I was in my late 20s when our three sons were babies and toddlers. I remember them catching every bug going around, including a wild six weeks when they decided to get chicken pox, one at a time, but I don't remember being felled so completely by a cold as I was felled last week.

It's Science Week, and I celebrated by reading a report on the evolution of the immune system, which put into words what my family has demonstrated in practice over the past few weeks.

Children "acquire viral, bacterial and parasitic infections that have to be fought off and controlled by immune responses" that promote recovery and result in "immunological memory".

"Thus, over time, protection provided by the immune response increases and young adults suffer fewer infections," the report said.

But at the other end of the spectrum, "as age advances, the immune system undergoes profound remodelling and decline, with major impact on health and survival".

Good to know. All is right with the world. The baby is supposed to be an extraordinarily efficient bug-distribution unit because her immune system can, and should, respond in the way it did, while I'm now in a body with an immune system "undergoing profound remodelling", where a cold can leave me ragged for a couple of weeks.

When I was pregnant with my eldest son I came down with glandular fever, and promptly passed it on to my father. I don't know who fared worse out of that, but I do remember my father's extraordinary, and profound, joy at becoming a grandfather for the first time, even after having 11 children of his own. And we do survive.