Two Latin American countries are investigating whether outbreaks of the mosquito-borne Zika virus are behind a rise in a rare and sometimes life-threatening nerve condition that can cause paralysis and leave victims on life-support.
The Zika virus has already been tentatively linked to a rash of microcephaly, a birth defect in which babies are born with unusually small heads. And while the mechanics of how the virus may affect infants remain murky, authorities in Brazil, Colombia and El Salvador are urging women to avoid the risk by postponing pregnancies.
The US Centers for Disease Control and Prevention advised pregnant women to reconsider travel to countries with Zika outbreaks, and on Friday it expanded the warning to 22 destinations, most in Latin America and the Caribbean.
The rise in cases of Guillain-Barre has also alarmed health officials region-wide. The nerve disorder causes muscle weakness that generally begins in the legs and spreads to the arms and face, and can cause numbness, trouble walking and even limb paralysis.
While most people recover in weeks or months, in severe cases the muscles used for breathing weaken so much that patients require life-support.
Anyone of any age can get Guillain-Barre, although it is very rare. It is thought to be triggered by an infection – something as simple as food poisoning – and happens when the immune system attacks the body’s own nervous system.
Researchers have been wary of Zika since French Polynesia noted a jump in Guillain-Barre and microcephaly cases in tandem with an outbreak of the dengue-like virus, though the populations were far smaller than in the recent outbreaks.
The World Health Organisation said authorities in El Salvador reported 46 cases of Guillain-Barre in just five weeks, from December 1 to January 6. The full-year average for the country is 169 cases. Of 22 patients for whom there was information, at least 12 had experienced a rash-fever illness in the 15 days prior.
Brazilian officials are also probing a near-simultaneous rise in Guillain-Barre and Zika, which was first identified in the country last May. It is believed that Zika may have arrived through a tourist at the 2014 World Cup or an international canoeing event the same year.
Zika originated in Africa and expanded to parts of Asia. When it was first detected in Brazil, health officials were not initially alarmed since the virus appeared to be like a less potent form of dengue. But then came the spike in microcephaly: since October the country has recorded 3893 suspected cases, compared with fewer than 150 for all of 2014.
Brazilian officials say they are convinced of a link. International health bodies say it is not yet scientifically established, but they are on alert. The CDC said Friday it issued its travel advisory “out of an abundance of caution”.
Earlier this week El Salvador recommended women avoid getting pregnant for the next two years, and some are taking that advice.