Understanding the Zika virus

Robert Anderson, professor of microbiology and immunology at Dalhousie University, demonstrates how vaccines are researched (Photo: Grace Kennedy)

By Grace Kennedy

In mid-February, Brazil’s army will march on its own country. Going from home to home, nearly 220,000 soldiers will hand out pamphlets and give advice on how to eliminate mosquito breeding grounds.

It is a war against what Brazilian Health Minister Marcelo Castro calls Brazil’s public enemy number one: the Aedes Aegypti mosquito.

This campaign is Brazil’s most recent attempt to curb the spread of the mosquito-borne Zika virus. In May 2015, the first cases of Zika were found in Brazil. Since then the virus has spread to more than 20 countries – including Colombia, Ecuador, El Salvador, Haiti, Mexico and Puerto Rico – and will continue to move across the Americas.

Most people infected with the virus will absent-mindedly scratch their mosquito-bite, not knowing a virus is circulating inside them. The other 20 per cent may get a fever or a rash. Their joints and muscles may be sore; they could have a headache and their eyes may be red.

This is not why agencies like the Centers for Disease Control and Prevention have issued travel warnings, or Brazil has called out the army.

Since the start of the Zika virus outbreak there have been more cases of Guillian-Barre syndrome and a birth defect known as microcephaly in affected countries. This is why the world is taking notice.

The virus is relatively new. The first Zika infection in humans was discovered in Africa in 1952, and since then there have been periodic outbreaks in French Polynesia, New Caledonia and the Federated States of Micronesia.

But this outbreak is the biggest – and the first time the virus has made it into the Americas. More than one million Brazilians have been infected and with no vaccine available, that number is only going to increase.

“New infectious diseases are emerging and re-emerging all the time,” said Joanne Langley, associate director of the Canadian Centre of Vaccinology and professor of pediatrics at Dalhousie University. “So we have to be alert to it.”

Sidebar Zika

The symptoms: Guillian-Barre

A tingling in your toes, weakness in your legs. It’s the first signs of Guillian-Barre syndrome – a disorder that causes the immune system to attack the nervous system.

Guillian-Barre has occurred in some individuals with Zika, said Robert Anderson, a professor of microbiology and immunology at Dalhousie, but it can also occur because of other infections.

The syndrome is the result of an overzealous immune response to an infection; although some cases are life threatening, most result in a full recovery.

In just five weeks, El Salvador reported nearly a quarter of its yearly average of Guillian-Barre cases during the Zika outbreak.

The symptoms: microcephaly

When a pregnant woman is infected with a virus, it gets into her blood stream “and it’s spread to the infant,” Langley said. “It actually goes to a number of their organs because they’re being exposed to quite a substantial load of virus. And so the brain can get infected and it stops growing or it grows less.”

This lack of growth is called microcephaly. Babies born with microcephaly have smaller than normal heads; this is because the size of the head depends on the size of the brain – and their brains aren’t growing. And when the brain doesn’t grow, neither does the person’s capacity to learn and function.

“If someone has severe microcephaly they really stay as an infant,” Langley said. “Physically they would grow, but they wouldn’t acquire the ability to speak or hear or care for themselves.”

The number of microcephaly cases recorded in Brazil since October 2015 is now over 4,000. In 2014, there were less than 150 cases. There is no confirmed link between Zika and microcephaly, but the correlation makes a strong case.

So far, the only way to stop Zika is to prevent mosquito bites.

And so, on Feb. 13, the Brazilian army will take to the streets, ready to arm citizens with knowledge about the prevention of mosquito bites.