Episode 5 – What is La Niña? Can it really lead to diarrhoea?

In this episode, Aleena and Janine respond to a listener question (#exciting!): Deepak got in touch to ask them to explain the La Niña weather cycle that he keeps hearing about in the news in Australia this Summer. They start by breaking down the science that causes La Niña (and El Niño) weather patterns across the globe. Then they go deeper into some research showing how this global weather system can lead to or worsen diarrhoeal disease and even increase the likelihood of future pandemics. Meanwhile, Aleena explains why she can now recite the Nato Phonetic Alphabet, and Janine regales us with tales of a card game for any fellow evolutionary biology nerds!

La Niña? El Niño? What’s going on?

A La Niña phase is triggered when strong trade winds, blowing from the eastern to western Pacific, drive warmer ocean water towards the Australian and Asian regions. Because the water on the Australian side of the pacific is now warmer, there is more evaporation, leading to higher cloud cover and increased rainfall. This leads to a higher likelihood of flooding and cyclones, plus cooler daytime temperatures in the Australian region. At the same time, we will see basically the opposite weather patterns – hotter and dryer – in the Southern US, Central and South America.

If the trade winds slow down or reverse, this triggers the opposite weather pattern: El Niño. Here we see hotter and dryer weather in the Australian region and the opposite patterns in the Southern US, Central and South America.

Check out these excellent sources to learn more: Bureau of Meteorology in Australia (including this awesome video), the ABC in Australia and the National Ocean Service in the US.

Diarrhoeal disease

Diarrhoeal disease is a serious problem in many parts of the world. It’s a leading cause of death in children under 5 years old, and over half a million kids die from diarrhoea each year. Facts from the WHO here.

What happened in Tuvalu?

An unusually strong La Niña period brought severe drought to Tuvalu in 2011. At the same time Tuvalu had a serious outbreak of diarrhoea. What happened and how? This epidemiological study sheds light on how La Niña and other serious weather events impact human health.

Emont, J. P. et al. (2017). Epidemiological Investigation of a Diarrhea Outbreak in the South Pacific Island Nation of Tuvalu During a Severe La Niña-Associated Drought Emergency in 2011. The American Journal of Tropical Medicine and Hygiene, 96(3): 576-582.

The weather and flu pandemics

Two additional studies exploring potential links between La Niña and El Niño and the timing and severity of influenza pandemics:

Shaman, J. & Lipsitch, M,. (2013). The El Niño–Southern Oscillation (ENSO)–pandemic Influenza connection: Coincident or causal? Proceedings of the National Academy of Sciences,110 (Supp 1): 3689-3691.

Oluwole, O. S. A. (2017). Deterministic Chaos, El Niño Southern Oscillation, and Seasonal Influenza Epidemics. Frontiers in Environmental Science, 5: Article 8.

What brought out our inner square?

Janine has been waiting several years to get the game Go Extinct for her child. Touted as “evolution meets card game”, she simply must have it. But when the time finally comes, it is very hard to track down… but does that stop her? Heck no! She manages to secure one and now her 8-year old can explain terms such as “most recent common ancestor” and “evolutionary clade” and is genuinely having fun while doing so. Aleena learned a few things too!

Meanwhile Aleena explains her recent crash course into the Nato Phonetic Alphabet. The reason? The next time Aleena is on the phone to her bank she will be able to clearly communicate how to spell her 10-letter Polish surname. She only wishes she’d learned this skill 20 years ago.

Image by RUSLAN BOGDANOV on Unsplash

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