How did disease add to NZ's blackest year?

Soldiers walk over the mud and water-filled holes on duckboards near Passchendaele in October, 1917. Photo / File

Could better medical interventions have helped lower the death toll of New Zealand's blackest year of World War 1?

It's possible, Kiwi researchers have suggested, yet the loss of life to disease in 1917 paled in comparison to the horrific butcher's bill of three bloody battles.

In a paper published today in the New Zealand Medical Journal, researchers have analysed casualty figures from what was our military's worst ever year for loss of life.

One third of the more than 16,000 New Zealanders who died during the whole of the war fell in 1917, with injury deaths accounting for more than 92 per cent.

Most of those involved outright death - where the soldier was "killed in action" - with a smaller proportion having "died from wounds" following medical treatment, potentially weeks or months later.

Much of those deaths could be put down to three major battles Kiwis fought that year, notably the Battle of Messines, in June, and the Third Battle of Ypres, in October.

On our "darkest day" - October 12 - 846 New Zealanders were killed on the Bellevue Spur, while attempting to capture the Belgian town of Passchendaele, proving the biggest loss of Kiwi lives ever in a single day.

By constrast, diseases in 1917 accounted for 250 deaths, or 4.5 per cent of that year's fatal casualties, although the true figure was probably higher, wrote study authors Professor Nick Wilson, of Otago University, and military historian Glyn Harper, of Massey University.

For example, they noted, if all of those poorly classified deaths could be put down to disease, then the proportion would have risen to 6.3 per cent.

In a 20 per cent random sample of the disease-related deaths, the dominant cause was pneumonia or bronchitis, accounting for just under a third, followed by tuberculosis, accounting for 16 per cent.

"Of the disease deaths occurring in the North Hemisphere, such deaths were statistically significantly more common in the Northern Hemisphere's winter months," they wrote.

"This particular winter was reported as being a particularly severe one."

Adding to that was the fact that Flanders' water table was only just below ground level, so the cold was combined with near-constant wet conditions in front line positions.

The extent to which any fraction of those disease deaths were preventable with knowledge of the day was speculative, they said, yet some could be put down to crowding, which was also a factor in earlier deaths at the Trentham military camp, and later ones implicated with 1918's pandemic influenza outbreak.

"However, 1917 did not see events such as the large outbreak of dysentery... seen in the Gallipoli campaign in 1915," they wrote.

"In conclusion, the year 1917 was the worst year from a mortality perspective in the country's military history.

"This very heavy mortality burden was partly driven by three major battles, with a relatively small role played by disease."

The paper followed an earlier opinion piece by Wilson, who wrote factors like poor military leadership and helmet design also played a part in deaths.