Scientists 'can't explain' Black Death plague outbreak in Madagascar.

PLAGUE warnings were being issued for nine countries in south-east Africa this week, as authorities rushed to contain an outbreak of Black Death.

It's the same virus that led to one of the most devastating pandemics in human history, killing an estimated 25 million people in Medieval Europe.

The recent outbreak is believed to have started in Madagascar, an island nation off the African coast, and at least 1300 people have been infected.

It's a serious bacterial infection transmitted by fleas, and can be easily treated with antibiotics, but so far 124 have been reported dead.

"Plague, though terrifying, is nothing new in Madagascar, where about 600 cases are reported annually," the World Health Organisation said on its website.

However, WHO officials warned there is "something different" about this outbreak, and "health officials couldn't explain it".

"Plague is a disease of poverty, because it thrives in places with poor sanitary conditions and health services," said Dr Arthur Rakotonjanabelo.

However, he said the plague had spread to new parts of the country, which hadn't seen the plague since at least 1950.

Global health authorities are constantly trying to predict the next outbreak - bacterial or viral - so it can be stopped before it becomes an epidemic or pandemic.

The Global Virome Project, which was proposed in 2016 and is just beginning to take shape, is one ambitious initiative which aims to find all viruses in birds and mammals that could spill over to humans in the next decade.

Meanwhile, the US Agency for International Development has spent the past eight years cataloguing threats, identifying 1000 new viruses.

However, experts estimate 99.9 per cent of viruses are still unknown.

A new Australian study, published this week by Jemma Geoghegan from Macquarie University and Edward Holmes from the University of Sydney, argued it's impossible to predict a global outbreak because there are too many variables.

They said efforts will fail because the enormous number of unknown viruses could evolve and appear in humans at any time.

"The [Global Virome Project] will be great for understanding more about viruses and their evolution, but I don't see how it'll help us work out what's going to infect us," Dr Geoghegan told The Atlantic's Ed Yong.

"We're only just coming to terms with the vastness of the virosphere."

Once a virus achieves human-to-human transmission, it's really just a matter of luck as to how severe and contagious it is, and whether or not it can be treated quickly.

EVOLUTION CAN BE GREAT, AND TERRIBLE

Both humans and diseases are constantly changing, so it's a bit like trying to hit a moving target from a moving car.

"We're trying to predict really, really rare events from not much information, which I think is going to fail," Dr Geoghegan said - and history agrees.

For example, scientists discovered the Zika virus in Uganda way back in 1947, and yet there was an outbreak on the other side of the world, in Brazil, two years ago.

The disease is spread by mosquitoes, and can cause severe birth defects in babies if the mother is bitten while pregnant.

Similarly, the Ebola virus was discovered in 1976 in South Sudan, but it claimed a reported 11,315 lives in west Africa three years ago.

It is highly infectious and spreads through transmission of bodily fluids, causing a gruesome death as the whole body haemorrhages.

Still other diseases emerge totally out of the blue.

One example is the SARS virus - a severe form of pneumonia - which broke out in China after a researcher accidentally caught it in a lab in 2002.

Another is HIV, a sexually transmitted virus which attacks the body's immune system, which has claimed an estimated 35 million lives in the past 40 years.

Probably the most famous of all is the Spanish Influenza pandemic, which killed up to 100 million people - or five per cent of the world's population - in 1918.

The other variable is changes to possible treatments - which vary widely depending if the outbreak is bacterial or viral.

Vaccines are undoubtedly the best way to treat viruses, because they require living hosts to multiply and can only really be fought off by the body's own immune system, but they are a prevention and not a cure.

Bacteria, on the other hand, can be effectively treated with antibiotics - however, health experts warn an "antibiotic apocalypse" is fast approaching, as overuse of drugs like Penicillin lead to a significant increase in drug-resistant infections.

DOES SCIENCE HAVE A WAY FORWARD?

Dr Geoghegan thinks the best way forward is to focus just on the "fault lines".

The Atlantic reports that means regions where people are more likely to be exposed to animal viruses because they are chopping down forests, setting up dense animal markets, hunting wild creatures for meat, or moving around a lot because of political instability.

However, others argue global scientific efforts shouldn't be so readily dismissed.

Professor Jonna Mazet, global director for PREDICT, a European Union organisation that aims to prepare for the "domino effect" in crisis situations, told Ed Yong it's too early to know how things will pan out.

She said if the same complaints had been made about meteorology a century ago, "we wouldn't have created the data that lets us forecast the weather, which we can do pretty well now".