Zika: Then, now, and tomorrow
Where do we stand one year after WHO announced Zika as a public health emergency? International spread has continued, while surveillance has improved. In line with WHO advice, innovative approaches to mosquito control are being piloted in countries and WHO will provide sustained guidance for effective interventions and support for families, communities, and countries experiencing Zika virus.
In 2015, the Zika virus outbreak in Brazil was yet another of the hundreds of disease outbreaks WHO records each year. When the first people with benign skin rash went to see their doctor, nobody could predict that Zika would invade an entire continent.
A rise in people with Guillain-Barré syndrome, a rare condition which can lead to near-total paralysis, was also observed. When the first babies were born with smaller than usual heads, mothers and families were overwhelmed by anxiety and dispair.
The world was puzzled and horrified. How could a virus carried by mosquitoes cause neurological disorders? By the start of February 2016, local transmission of Zika virus had been reported from more than 20 countries in the Americas, and a Zika outbreak was under way in Cabo Verde. On 1 February 2016, WHO declared the events a Public Health Emergency of International Concern.
A few days later, we issued the first Zika situation report. Situation reports include a classification of countries to characterize the level of virus transmission in given places over time.
This helps us to assess the risk of Zika virus infection and related complications, and to issue national, regional and global public health recommendations for residents and travellers backed up by data.
Every week since early February 2016, we have been publishing a summary of the cases of Zika, microcephaly and Guillain-Barré syndrome that Member States report to WHO. Based on the data we receive from countries, we see that Zika virus is here to stay.
Along with a guidance development group, WHO has revised the Zika virus country classification scheme. The revised classification can help public health authorities and policy-makers to assess the risk of Zika virus transmission related to time and place and according to the presence of the Aedes aegypti mosquito.
The assessments enable countries to issue public health recommendations as appropriate. For the first time, the revised classification includes a category for countries that have the Aedes aegypti mosquito but no known documented Zika virus transmission.
The Aedes aegypti mosquito is considered the main vector of Zika virus transmission because it sustains most Zika virus outbreaks. All countries with Aedes aegypti mosquitoes are at risk of Zika virus transmission, particularly in light of global travel. Zika virus may be imported by infected travellers into an area that may not have Zika virus transmission at that point of time.
If those travellers are bitten by local Aedes aegypti mosquitoes the mosquitos can transmit the virus to others, potentially setting off a cycle of transmission. We therefore strongly encourage all countries with Aedes aegypti mosquitoes to enhance early warning systems for Zika and related severe neurological complications, in particular Guillain-Barré syndrome and congenital Zika virus syndrome.