It starts with the usual symptoms of an infection: sore throat and fever, headache and muscle pain. But within hours, it’s clear it’s more than just flu. First comes the dizziness and fuzzy thought, then the seizures — and, for most, death.
Small wonder that health officials in the UAE have been warning anyone visiting the India state of Kerala about the outbreak of the Nipah virus there, and the need to exercise extreme caution.
Named after the region in Malaysia where it was first identified 20 year ago, this latest outbreak has so far claimed the lives of only a dozen or so people.
Even so, it’s devastating effect has led to Nipah being added to the World Health Organisation list of infections posing a global threat.
That puts it in the same notorious club as Ebola, Zika and Mers.
Fortunately, the evidence so far suggests that while it kills up to 75 per cent of those infected, Nipah is still relatively hard to contract.
On Wednesday, an Indian soldier was reported to have died of suspected infection by the virus.
According to AFP, the soldier was admitted to hospital in Kolkata on May 20, a week after returning from holiday in Kerala.
Previous outbreaks point to the need for direct contact with infected animals or patients.
However, a recent report by Indian medical experts ruled out bats and pigs as the primary source of the outbreak.
But the thing about viruses is that they evolve. There are already reports from the Kerala outbreak that Nipah has passed into fruit bats, which are contaminating fruit eaten by humans.
The race is now on to find treatments and vaccines before it evolves into something like the pandemic that struck exactly a century ago. While far less deadly that Nipah, the Spanish Flu virus spread like wildfire and between 1918 and 1920 killed an estimated 50-100 million people worldwide.
This devastating event continues to cast a long shadow over attempts to prevent viral epidemics.
Yet just as viruses evolve, so does scientific knowledge. And researchers are now starting to get the upper hand in the war against these microscopic terrorists.
When the Spanish Flu epidemic began, the very existence of viruses was unclear. Scientists only knew that some diseases were caused by agents so small they were invisible even using the most powerful optical microscopes.
It took the invention of the electron microscope in the 1930s to reveal their true nature: small strings of molecules wrapped in a protein bag.
Made from either DNA or its close relation RNA, those molecules allow the virus to hijack the genetic machinery of healthy cells and churn out new virus instead.
No one knows where viruses came from. Some scientists have seriously argued they may be from another world.
What is certain is that they pose a constant threat to on our planet. Reports of smallpox date back millennia, and during the 20th century alone that one disease claimed at least 300 million lives.
But it was also the first to be defeated by science. In 1980, WHO announced that its global programme of mass vaccination begun 20 years earlier had finally eliminated the disease.
Ever since, scientists have been working to achieve similar success with other viral killers.
And now there’s real optimism that success is within reach.
When the Ebola virus claimed its first victims in central Africa in 1976, it gained a nightmarish reputation. Up to 90 per cent of those infected died horrific deaths, bleeding to death while their organs disintegrated.
In 2013, Ebola tore across West Africa, killing more than 11,000 in a three-year epidemic.
Now it’s flared up again, claiming victims in the Democratic Republic of Congo. But this time doctors are fighting back, using an experimental vaccine developed by the US-based pharmaceutical company Merck.
While it’s not a cure, the hope is that it can dramatically slow the spread of the disease, allowing medics to focus on those infected.
Meanwhile, just last month the US National Institutes of Health announced the start of human trials of a treatment for another disease on the WHO's "Most Wanted" list: Mers.
First reported in Jordan in 2012, Middle East respiratory syndrome is caused by a so-called coronavirus, which triggers respiratory and kidney failure. Of the 2000-plus people who have contracted Mers to date, including the UAE's first case of the year reported on Tuesday, more than 1 in 3 have died.
The new trial will test the safety of a monoclonal antibody, a drug specially designed to seek out the virus in the body and disable it. Results are expected next year.
But the most potent weapon in the war against viruses is not a drug or a vaccine: it is surveillance.
Rapid detection of the very first cases allow those affected to be identified and quarantined — thus depriving the viruses of the one thing they all need to thrive: human hosts.
No matter how fast they evolve, if they cannot spread they will become extinct.
Since the WHO’s establishment of a global network of monitoring centres for influenza in 1952, it has arguably saved more lives than any medical treatment yet devised.
And it has probably already prevented at least one global pandemic.
In November 2002, Canadian epidemiologists came across rumours of a new disease that had broken out in southern China.
It was the first evidence for what became known as the Severe Acute Respiratory Syndrome (Sars) virus, which proved to be almost as dangerous as Spanish Flu.
By monitoring its spread, epidemiologists were able to help keep it contained, and when the outbreak ended in July 2003, Sars had claimed fewer than 800 lives worldwide.
The virus surveillance system is now so good that it detected the handful of Nipah cases within days, and triggered a global alert.
No one knows when or where the next potential pandemic will start. But our best hope of stopping it lies not in miracle cures but in vigilance.