(February 5th, 2016) Just a short while ago, the fight against the Ebola virus was won. Now, a new virus is frightening the world, in particular people in the Americas. We contacted two experts to learn more about this international emergency known as the Zika virus.
As of Monday, 1st February 2016, the WHO has declared the Zika virus outbreak to be a “public health emergency of international concern”. The virus is believed to “constitute a public health risk (…) through the international spread of the disease” and that “a coordinated international response” is required to combat it. This puts the Zika virus in the same category as the Swine Flu pandemic of 2009, the resurgence of polio in 2014 and the Ebola outbreak of the same year.
The Zika virus is an RNA virus of the family Flaviviridae and is related to the viruses causing dengue fever, yellow fever and Japanese encephalitis. Originally identified in a rhesus monkey in the Zika Forest of Uganda in 1947, it was first reported in humans in Uganda and Tanzania in 1952. Since then, small scale outbreaks have been recorded in Africa, the Americas, Asia and the Pacific. The virus is primarily transmitted via the bite of an infected mosquito (Aedes aegypti or A. albopictus), although secondary transmission through sexual contact has recently been reported in Texas, USA.
An infection is typically rather mild and manifests itself in every fifth infected individual. It lasts for two to seven days and symptoms include fever, conjunctivitis, rashes, malaise, headache, muscle and joint pain. Those infected are advised to take rest, increase their fluid intake and consume common analgesics and antipyretics. Specific medicines or vaccines are presently not available.
In recent times, the Zika virus has made headlines all over the world due to its latest outbreak in the Americas. Not only has the virus spread rapidly in the span of just a few months (25 countries as of 29th January 2016), its apparent association with microcephaly (as of 23rd January 2016, 4,180 suspected cases of microcephaly have been potentially linked to the virus) and Guillain–Barré syndrome, has caused global alarm.
Lab Times contacted Jonas Schmidt-Chanasit, head of the Arbovirus laboratory at the Bernhard Nocht Institue for Tropical Medicine in Hamburg, Germany and Oliver Brady of the Spatial Ecology and Epidemiology Group at the University of Oxford, England, to better understand this outbreak.
The current explosive spread of this virus can be attributed to the widespread mosquito vector and the non-immune human hosts, says Schmidt-Chanasit. “It is currently unknown why this Zika outbreak has gone on to infect so many people in comparison with outbreaks of the disease in the past. What we do know is that Zika has been introduced into a continent with dense urban cities, a highly efficient mosquito vector in Aedes and with lots of people moving between countries at an ever faster rate. However, the disease is also found in Asia and it is unclear why there has not been an outbreak of comparable size there,” explains Brady.
There has been speculation among the general public that the Zika virus responsible for the ongoing outbreak is a mutated, more potent one. How much truth does this statement hold? Both scientists agree that this is not likely to be true. Oliver Brady says, “There have been no known mutations of Zika that would make it more transmissible or deadly. Mutations of this kind are relatively rare in this group of viruses and we would not expect this to be a primary concern. The virus in its current form already poses a significant public health threat and understanding more about the virus in its current form should be the priority.” Jonas Schmidt-Chanasit adds, “There is no evidence, if specific mutations alter the pathogenicity of the virus or lead to more efficient replication of the virus in the mosquito vector. Thus, there is no ‘specific’ cause for concern. However, viruses always mutate and I can’t predict the future.”
Containing the mosquito vector is key to controlling this outbreak, agree both researchers. A lot is known about the vector as it is also the vector of other major diseases, such as dengue fever, yellow fever and Chikungunya, explains Brady. “The main challenge is that the virus is transmitted by the mosquito Aedes, which lives in close proximity to humans. The mosquito typically lays eggs inside people's houses in any container that can hold water. These can be as small as a flowerpot, or a discarded tyre in the back garden. Eliminating all these mosquito habitats in a tropical city with poor garbage disposal is a massive challenge and one that can only be tackled, if the whole community is engaged in big community clean up campaigns,” he elaborates.
It currently remains unclear if the Zika virus interacts or associates with other viruses, such as dengue. Brady tells us, “We currently do not know what the consequences of co-infection with dengue and chikungunya are. Given the widespread circulation of both these viruses in South America at the moment, it is likely that this does occur and understanding what clinical signs patients have may be important,” Schmidt-Chanasit thinks that “this is a very important question and our future research projects will focus on these questions. There is no information available yet”.
International experts forecast that the virus will continue to spread into all countries and territories of the Americas where the Aedes mosquito vector is present. Outside of the Americas, countries like France, Spain, Indonesia and Thailand have also reported cases of infected travellers returning from the affected areas. In the light of the current situation, some countries have asked couples to delay pregnancies and the US Centers for Disease Control has advised pregnant women not travel to the affected region. Especially in Brazil, where the largest number of cases has been reported (about 1.5 million) the Zika virus has cast a dark shadow on the ongoing carnival celebrations and the upcoming Summer Olympics in August 2016.
Picture: CDC/Cynthia Goldsmith (transmission electron micrograph of Zika virus), Final destinations of travellers departing Brazil by potential for autochthonous Zika transmission (The Lancet, 23 Jan, 2016)