Zika has become a pandemic in a manner Ebola never was
Africa may have buried the final corpses from the Ebola outbreak, but another continent is already mourning the unborn victims of the next global disease epidemic.
The Zika virus, long established in Asia and Africa, and sweeping through the Americas, has been linked to the birth of babies with abnormally small heads. And it qualifies geographically for the term "pandemic" in a way that Ebola never did.
While the terror of Ebola was largely confined to three countries - Guinea, Liberia and Sierra Leone - Zika already affects 23 countries and is likely to spread wherever its carrier, the Aedes aegypti mosquito, roams. On Monday, the World Health Organisation (WHO) declared it a Public Health Emergency of International Concern, as Ebola and swine flu were, in a move that will push governments and public health bodies to issue travel warnings, heighten surveillance and accelerate vaccine development.
Zika is not contagious in the way that Ebola is, nor is it as lethal (fever, rash, joint pain) but it appears to strike in an especially cruel way - depressing brain growth in babies born to infected mothers. And like so many pathogens that preceded it, the Zika virus has seemingly whirled out of nowhere, reinforcing how difficult it is to predict confidently which ones will go rogue.
It only appeared in Brazil last May and is forecast to affect up to four million across the Americas by the end of this year.
Before Brazil notified the WHO of the unusually high number of babies born with microcephaly at the end of last year - a red flag which its health system deserves some credit for waving - Zika was barely on the radar outside Africa and Asia, where people enjoy relative immunity.
It was never expected to seed the next global health panic. That honour, according to expert forecasts, should have gone variously to bird flu, West Nile virus or chikungunya virus, none of which has yet induced panic.
Zika belongs to the same family of viruses, called flaviviruses, as Yellow Fever, Dengue and West Nile, all of which are associated with encephalitis, or brain inflammation. All of which we are familiar with. None, though, had ever been shown to damage a foetus.
And if an unknown virus takes root in areas of the world with poor healthcare and patchy surveillance, it can take time for the outbreak to be noted - especially when symptoms are mild or non-existent, as with Zika. Indeed, the virus had a nine-month advantage on doctors because it is the gestational time for a baby. It is unsurprising, therefore, that the WHO is having to play catch-up.
For, as yet, there is no cure or vaccine for Zika
Given our poor record of predicting which diseases will spiral out of control - Ebola, swine flu and SARS all caught observers by surprise - the WHO has to focus on surveillance and firefighting.
Viruses are evolving all the time, multiplying and expanding their empires thanks to climate change, urbanisation and international travel. Fluid borders between city and countryside, especially in developing countries, bring humans into contact with new diseases lurking in rural hosts, such as bats or monkeys. There are limitless opportunities for viruses to gain traction.
But humans are clever. We can try to develop broad-spectrum antiviral drugs to counter a range of viruses instead of a "one-bug, one-drug" approach. We can attack mosquitoes with pesticides; we could one day deploy genetically modified mosquitoes, weaponised with an offspring-killing gene, to breed with virus-bearing mosquitoes.
Zika is merely a new front in our millennia-old war against the pathogens - and we need to find new ways of biting back. (© Daily Telegraph, London)