In the big national crises over more than a century, cartoonists have been the people the authorities call in to help get a message across.

David Pope's cartoon on the front page sits well in this honourable tradition.

It's witty - Masking for a Friend is a nice play on words. And endearing, with the mischievous platypus masking up.

It's informative - did you spot the reference to social distancing in the emu's "hand" and the sanitizer in the pouch of the kangaroo?

Above all, it's striking.

If a picture is worth a thousand words, how many must a cartoon be worth, particularly on crowded social media where everything competes for a nanosecond of our attention?

Cartoons reach people whom words pass by. They are easily and instantly understood. They speak a common language. Even if you don't understand the words, the picture tells the story - as it does with David Pope's creation.

In times of war and plague, the cartoon comes into its own.

Think of the illustration by the children's author May Gibbs for a poster during the Spanish flu epidemic in 1919.

It appeals to both adults and children and has all those hallmarks of being informative, witty and striking.

It struck a chord across the classes. "The illustration uses the popular icon created by May Gibbs, the 'gumnut baby', one of the bush babies series that made her famous," as the National Archives of Australia description puts it.

"Gibbs used distinctly Australian motifs at a time when the Australian bush was an important symbol of national identity."

David Pope's work uses the same sort of images, popular, uniquely Australian animals.

Twenty years after the outbreak in 1919, flu was still rampant and again the cartoon was used to educate without lecturing.

All kinds of home-spun (and useless) methods were being used by people, particularly parents, to try to cure the flu. A nose grip was one suggestion for a baby.

It prompted a cartoon published in 1937 which depicted parents taking the advice of doctors and of the health minister, William Hughes, each picture depicting a folk remedy like "smearing the nostrils with sulphate of zinc".

The cartoon ends by suggesting that the treatments were doing more harm than good and that fresh air would be better than all the remedies the parents tried.

Or nearer our own time, think of the Life. Be in it public health campaign from 1975.

The aim was to get Australians, particularly Australian men with beer guts, off the sofa and onto their walking legs.

One black-and-white cartoon by Alex Stitt titled Norm's walk showed Norm in four boxes: sitting in an armchair with his legs up and a can of beer in his hand; Norm getting out of his chair with the "Life. Be in it" slogan on the TV he's watching; Norm stepping away from the television; and finally Norm walking.

Norm became something of a cult - but there is a big caveat: was it the slob as hero?

"By 1977, when this cartoon appeared, the campaign had created a broad awareness of the benefits of increased participation in low-key physical activity," according to the National Archives.

"However, its success in prompting behavioural or attitudinal change is less certain.

"While death rates from cardiovascular disease have fallen steadily since 1977, the number of Australians living with cardiovascular disease and obesity has increased."

So cartoons have impact. They convey a message and change minds (if not always in the right direction).

There has been one study of the effectiveness of using them in a public health campaign. Researchers compared attitudes to smoking among groups of teenagers in Hong Kong. Some saw anti-smoking cartoons and some didn't.

The academics concluded that the posters with the cartoons "did decrease anti-smoking behavioral intentions".

But not all types of cartoon worked: "The better liked, more humorous, and more frightening posters did not produce increased anti-smoking attitudes or behavioral intentions".

Cartoons alone can't change minds but they do have an influence - in plague but also in war.

The great New Zealand cartoonist, David Low, migrated to London between the wars.

When the Second World War started, he helped keep Britain united when it and Australia and other allies in the Empire stood alone.

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When France fell to the Nazis, the Evening Standard in London published a Low cartoon depicting a grim-faced British soldier standing on a rock in a stormy sea shaking his fist at a squadron of enemy bombers approaching across a pitch-black sky. The caption read "Very well. Alone." It caught the mood exactly.

Low did something truly amazing: he got under Hitler's skin.

Right through the 30s, Low started depicting Hitler as a ridiculous figure - laughable even (and even more so with Mussolini).

The aspiring despot first appeared in a Low cartoon on September 27, 1930, with the caption "LITTLE ADOLF TRIES ON THE SPIKED MOUSTACHE".

Michael Foot, the editor of the Evening Standard, said: "Low contributed more than any other single figure and as a result changed the atmosphere in the way people saw Hitler."

So successful was David Low at parodying Hitler that the British government thought he might be impeding the chance of a negotiated peace.

As the cartoonist described it: "Once a week Hitler had my cartoons brought out and laid on his desk in front of him, and he finished always with an explosion.

"So the Foreign Secretary asked me to modify my criticism in order that a better chance could be had for making friendly relations.

"The Foreign Secretary explained to me that I was a factor that was going against peace.

" 'Do I understand you to say that you would find it easier to promote peace if my cartoons did not irritate the Nazi leaders personally?' 'Yes,' he replied."

"So I said, 'Very well, I don't want to be responsible for a world war.'

" 'But', I said, 'It's my duty as a journalist to report matters faithfully and in my own medium I have to speak the truth. And I think this man is awful. But I'll slow down a bit.'

"So I did."