In this transmission electron micrograph of Zika virus, the arrow indicates a single virus particle. Courtesy: U.S. Centers for Disease Control and Prevention.

Zika virus is a flavivirus, as are yellow fever, dengue and West Nile viruses. But none of those other viruses are known to cause microcephaly, which makes the Zika-microcephaly link “surprising,” according to Dr. Hugh Pennington.

Dr. Pennington, an emeritus professor of bacteriology at the University of Aberdeen, made that observation in a recent London Review of Books blog post.

“Diseases caused by the other flaviviruses have been intensively studied for many years without microcephaly turning up as a complication,” he wrote. “It hasn’t been clearly evident in Zika virus outbreaks elsewhere in the world. But flaviviruses mutate in real time. The classic example is West Nile virus. Isolated at the Rockefeller Yellow Fever labs in Uganda in 1937, like Zika it remained quiet for years. Then in the mid-1990s it got nastier, causing severe brain disease with epidemics in North Africa and Southern Europe. It took off in New York in 1999, and spread rapidly across the continent.”

But Dr. Pennington also noted that microcephaly has many causes and is not new, even in Central and South America, where individuals with the condition appear on bas-reliefs on Aztec temples.

“So far, the link between its [microcephaly] increase and Zika infections is only coincidence,” and firm evidence of the link will be hard to come by, he added.

A recent report by Brazilian clinicians, reported in the U.S. Centers for Disease Control and Prevention’s (CDC’s) Morbidity and Mortality Weekly Report, examined the first 35 cases of microcephaly reported to a registry established to investigation the link. They said that more study will be needed to confirm the connection, but noted that CDC recently tested samples from four pregnancies – two that ended in miscarriage and two that went to term but the infants who had microcephaly died shortly after birth. All four cases were from Brazil and were positive for Zika virus infection. The virus was present in the brains of the full-term infants, and genetically matched the Zika strain currently circulating in Brazil.

“The full spectrum of outcomes that might be associated with Zika virus infections during pregnancy is unknown.” – CDC

“Studies are under way to investigate the association of Zika virus infection and microcephaly, including the role of other contributory factors (e.g., prior or concurrent infection with other organisms, nutrition, and environment),” according to CDC’s current interim guidelines for pregnant women during a Zika outbreak.

“The full spectrum of outcomes that might be associated with Zika virus infections during pregnancy is unknown and requires further investigation.”

Meanwhile, former Canadian politician and diplomat Stephen Lewis sort of congratulated the World Health Organization (WHO) on declaring the apparently Zika-associated cases of micocephaly a “public health emergency of international concern.”

In the weekly video column he prepares for AIDS-Free World, an international advocacy organization of which he is co-director, Lewis said WHO has somewhat rehabilitated its reputation after it “failed lamentably” in responding to the Ebola crisis of the last few years.

UNICEF is MIA. – Stephen Lewis

But he added, “They are, as always, delayed – they’re late. It should have been done several months ago in 2015” at the time of the first reports of a Zika outbreak in Brazil. (Ed. note: Or possibly in 2007 where there was an outbreak in the South Pacific, or 2013 in French Polynesia with the first reports of a possible association with Guillan-Barré syndrome?)

Lewis also noted that UNICEF is missing in action on the Zika front: “UNICEF should be cheek-by-jowl, shoulder-to-shoulder with WHO, making pronouncements on what is to be done.”~TM