GENEVA: Local Zika virus transmission cases have been reported in 47 countries, a senior official of the World Health Organization (WHO) said.
Bruce Aylward, the WHO Executive Director for Outbreaks and Health Emergencies, said there exists “accumulating evidence” of a link between the Zika virus and two neurological disorders, microcephaly and Guillain-Barre syndrome, reported in nine of 47 countries hit by Zika fever.
“Since the public health emergency of international concern was declared back in February, the evidence that there may be a causal relationship that has continued to accumulate,” Aylward told a briefing in Geneva.
Aylward said that recently published studies in the Lancet on microcephaly and by the US Centers for Disease Control on Guillain-Barre strengthened the case that the mosquito-borne Zika virus is responsible.
“We’re now in the high season for dengue virus transmission in the southern hemisphere, that started a month or so ago,” Aylward said. “We believe because it’s the same vector, that this would be the high season obviously for Zika transmission as well.”
The WHO’s Emergency Committee will meet on March 7 to 9 to review “evolving information” and its recommendations on travel and trade in what is thought to be high season for transmission of the mosquito-borne virus in the southern hemisphere.
Zika virus was isolated in 1947 in the Zika forest of Uganda. Last May, it began to spread rapidly in Brazil, then gained ground in other countries of South and North America. Health officials report the virus penetrating 21 of 55 countries across the western hemisphere.
Medical professionals note special concern for infected pregnant women, whose children risk developing brain-damaging microcephaly.
The United Nations said a study published this week was the strongest piece of evidence yet that that the Zika virus causes the neurological disorder Guillain-Barre Syndrome, but more research was needed.
Aylward said the study from the medical journal Lancet which focused on a small sample of people in French Polynesia provided compelling evidence that Zika triggers the syndrome.
“This is the strongest evidence so far that this may be a causal relationship,” Aylward told journalists, referring to Zika’s link to GBS, which causes paralysis and even death in extreme cases.
But, he said, WHO needed to see similar studies replicated in other areas with the same findings.
Aylward added that evidence had also “continued to accumulate” in multiple studies linking Zika to microcephaly, a serious birth defect in which a baby is born with an abnormally small head and brain.
Zika, which is spreading rapidly in the Americas, is usually no more harmful than a bad cold or mild flu, but global anxiety about the mosquito-borne virus has been driven by its probable link to microcephaly and GBS.
“When we look at the evidence… it is all going in one direction,” Aylward said.
The case for the link was made stronger by the lack of evidence pointing to other possible causes for rising cases of microcephaly and GBS, Aylward added.
Nine countries in central and South America affected by the Zika outbreak have recorded an elevated number of GBS cases, according to WHO.
Brazil, which has registered an estimated 1.5 million Zika infections in the current outbreak, has seen 641 cases of microcephaly since October.
Brazil typically reports 150 cases of microcephaly per year.
WHO will next week host a meeting in Geneva to review the findings of the latest research on Zika.
Aylward, who was the UN agency’s pointman on the Ebola epidemic in West Africa, described the Zika outbreak as “one of the most challenging situations” he has confronted.
The response, he said, has been complicated by the previously sparse information about Zika and the fact that, until recently, there had been no understanding of connections between Zika, microcephaly and GBS.