WEEKS before the coronavirus spread through much of the world, parts of Africa were already threatened by another kind of plague – the biggest locust outbreak some countries had seen in 70 years.

Now the second wave of the voracious insects, some 20 times the size of the first, is arriving. Billions of the young desert locusts are winging in from breeding grounds in Somalia in search of fresh vegetation springing up with seasonal rains.

Millions of already vulnerable people are at risk. And as they gather to try to combat the locusts they risk spreading Covid-19 – a topic that comes a distant second for many in rural areas. It is the locusts that “everyone is talking about”, said one farmer in Uganda.

A failed garden of cassava, a local staple, means hunger. Such concerns are reflected across countries like Kenya, Ethiopia and South Sudan, Djibouti, Eritrea, Tanzania and Congo.

The UN Food and Agriculture Organisation (FAO) has called the outbreak, caused in part by climate change, “an unprecedented threat” to food security and livelihoods. “The current situation in East Africa remains extremely alarming as ... an increasing number of new swarms are forming in Kenya, southern Ethiopia and Somalia,” a new FAO assessment said.

Favourable breeding conditions throughout May mean there is likely to be another new round of swarms in late June and July, coinciding with the start of the harvest season.

The UN has raised its aid appeal from 76 million US dollars (£61m) to 153m (£123m), saying action is needed before more rainfall fuels further growth in locust numbers. So far the FAO has collected 111m (£89m) in cash or pledges.