Eastern Mediterranean weather patterns give clues to reducing deaths from flu worldwide, scientists say.

Each year between a quarter of a million people and half a million people die from flu or influenza, depending largely on how virulent each new strain of flu is. [Covid-19 is even deadlier: over a million people have been reportedly killed by the pandemic this year so far.]

Predicting which strain of flu will be predominant, and when it will arrive in each country, is vital to mounting a strong national defence. A different or tweaked vaccine is needed for each strain of flu, and it needs to supplied to the population to last the right amount of time.

Outbreaks of flu can also lead to greater deaths when a patient also has Covid, a recent British survey showed.

Now scientists claim to have found a new way of predicting when the flu epidemic will hit each country.

Writing  recently in the journal Science of the Total Environment scientists from Jerusalem, Tel Aviv and Karlsruhe (Germany) say they can predict when influenza outbreaks will occur — weeks, months and even years ahead.

The researchers specifically examined the weekly effect of a winter low-pressure weather system in the Eastern Mediterranean called “Cyprus Lows” together with precipitation, temperature, wind and humidity.

“Indeed, there is growing evidence that large-scale climatic modulations such as the El-Niño or La-Niña may influence the onset and peak of seasonal influenza in many regions across the globe,” the authors write.

The group was headed by epidemiologist and public health physician Hagai Levine, of the School of Public Health and Community Medicine at the Hebrew University in Jerusalem. The other members of the team were: Joachim Pinto from the Department of Tropospheric Research, Institute of Meteorology and Climate Research, Germany; Assaf Hochman, his colleague there, an Israeli postdoctoral fellow in climate research; Pinchas Alpert, professor emeritus in atmospheric sciences at Tel Aviv University; Mia Regev who heads the Health Systems Policy and Administration Programme at the University of Haifa; and Ziad Abdin, professor of clinical biochemistry and epidemiology at Al-Quds University in Jerusalem.

The researchers pieced together a picture of seasonal flu patterns in Israel and its neighbouring countries from 2008 to 2017 by analysing and comparing flu data from Israeli medical databases. Since the Palestinian Authority and Jordan do not have comprehensive medical databases, the scientists took data from Google Trends.

Putting that analysis together with weather data from the eastern Mediterranean, the researchers found a high correlation between precipitation, winter temperatures and the occurrence of flu.

Then they created a mathematical model to calculate future outbreaks and how long they may last, including highs and lows. They used the same method to make ‘predictions’ from data for the period of 2004 to 2007. It worked, allowing them to successfully ‘predict’ what actually happened – the timing of seasonal flu outbreaks in those years.

Levine and Hochman said their climate-based model could help public-health officials in other regions of the world improve how they prepare for outbreaks of flu and other climate-sensitive diseases.

“A better understanding of the correlation between weather and influenza regimes may improve vaccination policies and the allocation of medical resources. For example, health systems may relatively well estimate the timing of seasonal influenza outbreaks and improve the timing of seasonal vaccinations for the general population, particularly underprivileged populations such as the elderly,” said the authors.

Under the threat of climate change, recent studies led by Hochman indicate that by the end of the 21st century – if there is no lessening of greenhouse gas emissions — summers will be about 60 days longer, while winters could be shorter by about 60 days. These differences may lead to substantial changes in the timing of seasonal health hazards including seasonal influenza.