The resurgence of polio, a viral disease that can paralyze and cripple children, is so worrisome that the World Health Organization has declared a "public health emergency of international concern."
Practically, this means that people living in 10 countries where polio is currently spreading will have to show proof of vaccination before travelling abroad.
Symbolically, the WHO declaration is much more powerful: It is a warning that the three-decade effort to eradicate polio is in peril.
Until recently, polio was contained in three countries, but it is spreading largely because denying life-saving vaccination has become a weapon of choice for terrorists and despots.
The public health emergency is a thinly veiled diplomatic message that, if the world is serious about eradicating polio – and eliminating the need (and cost) to vacinate and then revaccinate 500 million children every year – there must be a co-ordinated push, including confronting vaccination's foes.
To date this year, the world has had 68 cases of polio – which may seem trivial on a planet with seven billion people.
But polio season – when the heavy rains come in the northern hemisphere – is fast approaching, and cases could increase exponentially. (Polio spreads primarily through contaminated water.)
Further, it is where the cases are occurring that is troubling.
When the eradication campaign began in 1988, polio was endemic in 125 countries. The initial goal was to be rid of it by 2000. We came tantalizingly close. The new target date is 2018.
Last year, only three endemic countries remained – Pakistan, Afghanistan and Nigeria. Recently, India, long the cradle of polio, was declared polio-free.
Almost simultaneously, polio began to gain a foothold in countries where it disappeared long ago, for a host of geopolitical reasons.
The WHO declaration on Monday named 10 countries where polio virus is now present: In addition to Pakistan, Afghanistan and Nigeria, they include Syria, Iraq, Cameroon, Equatorial Guinea, Ethiopia, Somalia and Israel. (Israel is an anomaly; polio virus has been detected in sewage but there have been no cases in people.)
The chief exporter of polio and impediment to eradication is Pakistan, where terrorists hunt and kill volunteers and health workers who conduct vaccination clinics. Things are not much better in Afghanistan.
(It is worth noting these hostilities began after the CIA used a sham vaccination campaign to get DNA on Osama bin-Laden's family, which led to his discovery and killing.)
Pakistan is where 59 of the world's 68 polio cases have occurred this year, and where vaccination rates are perilously low.
Just as troubling is the situation in Syria, a war-torn country where President Bashar al-Assad, has refused to allow polio vaccination in rebel-controlled areas, killing children with infectious diseases as well as bombs.
An estimated six million Syrians have been displaced, creating ideal conditions for polio to spread domestically and across the Middle East.
In Nigeria, radical Muslim clerics declared vaccination to be a U.S. plot to sterilize the young. In neighbouring Cameroon, the indifference of the country's leaders has allowed vaccination rates to plummet, and created a bridge for the virus to the Horn of Africa.
In fact, if there is a lesson to take from the rogues' gallery of polio-endemic countries, it is that disease flourishes where there is war, political unrest and poverty.
Polio, known as The Great Crippler, has always preyed on the most vulnerable, and now it has a helping hand from the ruthless.
When the polio eradication campaign began, more than 1,000 children a day were being infected. That number fell as low as 223 in 2012.
Last year, it climbed back again to 417 and, in 2014, who knows?
That will depend on the world's response to the public health emergency. The key is to contain, contain, contain, to stop the virus from spreading across borders and to get back to the mop-up operation of stopping its spread within endemic countries.
As Bruce Aylward, the Canadian who heads the polio eradication effort at the WHO is fond of saying: "Almost just isn't good enough with a virus like polio."