The Zika virus, possibly linked to serious birth defects in Brazil, has the potential to spread within the Americas, including parts of the United States, according to an international team of researchers tracking the spread of infectious diseases.

The Zika virus, native to parts of Africa and Asia, has for the first time been introduced into the Americas where it is spreading locally among people who have not travelled abroad. There is no vaccine against the virus nor any antiviral treatment.

Zika is generally a mild illness, spread by a day-biting mosquito. However, there is a worrisome association of infected mothers in Brazil giving birth to babies with small heads and underdeveloped brains (or microcephaly), according to Dr. Kamran Khan of St. Michael's Hospital, Toronto, Ontario, Canada.

There has been a 20-fold increase in the number of babies born with microcephaly since Zika first appeared in Brazil in May 2015.

The virus has since spread across more than a dozen countries in South and Central America and up into Mexico.

A case was confirmed in Puerto Rico in December in an individual who had not recently travelled, meaning he or she was bitten by a local infected mosquito.

The Centers for Disease Control say some travellers returning to the United States from Zika-affected areas have also been infected with the virus, which has the potential of allowing the virus to then spread locally.

"The summer Olympic Games in Brazil in August heighten the need for awareness of this emerging virus," Dr. Khan wrote in a research letter published in The Lancet. To predict where Zika might spread, Dr. Khan and his team mapped the final destinations of international travellers leaving airports in Brazil from September 2014 to August 2015.

Of those 9.9 million travellers, 65 per cent were going to the Americas, 27 per cent to Europe and 5 per cent to Asia.

Traveller volumes were greatest to the United States, followed by Argentina, Chile, Italy, Portugal, and France.

China and Angola received the highest volume of travellers in Asia and Africa, respectively.

Members of the team from Oxford University mapped the global geography of (Aedes species) mosquitoes capable of transmitting Zika virus and then modeled the worldwide climate conditions necessary for the virus to spread between Aedes mosquitoes and humans.

They estimated that more than 60 per cent of the populations of the United States, Argentina and Italy live in areas conducive to seasonal transmission of Zika virus.

By comparison, Mexico, Colombia and the United States have an estimated 30.5 million, 23.2 million and 22.7 million people respectively living in areas conducive to year-round Zika virus transmission.

Dr. Khan adds that with no vaccine or antiviral therapy available, possible interventions include (1) personal protection (i.e., repellent use); (2) daytime avoidance of mosquito bites (especially by pregnant women until more is known about the association between Zika virus infection and microcephaly) and (3) community-level mosquito surveillance and control measures.

"The world we live in is very interconnected now says Dr. Isaac Bogoch, a tropical infectious disease specialist at the Toronto General Hospital who contributed to the study. "Things don't happen in isolation anymore. Infections from the farthest corners of the world can quickly arrive on our doorstep."

Abstract
In May, 2015, locally acquired cases of Zika virus—an arbovirus found in Africa and Asia-Pacific and transmitted via Aedes mosquitoes—were confirmed in Brazil. The presence of Aedes mosquitoes across Latin America, coupled with suitable climatic conditions, have triggered a Zika virus epidemic in Brazil, currently estimated at 440 000–1 300 000 cases.1 Viraemic travellers have now introduced Zika virus into at least 13 additional countries, where susceptible Aedes mosquitoes have become infected and perpetuated local transmission cycles.

Funding for this study was provided by the Canadian Institutes of Health Research, the Wellcome Trust, the Bill & Melinda Gates Foundation, and the RAPIDD program of the Science & Technology Directorate, Department of Homeland Security, and the Fogarty International Center, National Institutes of Health.

About St. Michael's Hospital
St. Michael's Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in more than 23 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, and care of the homeless are among the Hospital's recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael's Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.

http://www.eurekalert.org/pub_releases/2016-01/smh-zvh011416.php#.Vpr_2x4gIsg.mailto

Recent articles related to microcephaly: Slow stem cell division causes small brain?

Return to top of page

Jan 21, 2016   Fetal Timeline   Maternal Timeline   News   News Archive   

Where is the Zika virus found?
Image Credit: Center for Disease Control