In the headlines this week, a major development in the fight against Zika — a first look at the virus itself. Scientists have determined the 3D structure of the virus, revealing critical insights that will likely help the race to develop effective treatments and vaccines.
Image courtesy of Purdue University/Kuhn and Rossmann Research Groups
Details of the new findings are published in the journal Science.
A team of researchers from Purdue University and the National Institutes of Health used cryo-electron microscopy to determine the virus’ structure at very close range – “near atomic resolution.” They used a strain isolated from a patient infected during the French Polynesia epidemic 2 years ago, but with new technology, their work now took just one month.
They found several similarities to other flaviviruses – including Dengue and West Nile — and that wasn’t surprising. But, they also discovered a variation on the virus’ surface, which could help explain how the virus works to attack cells and cause infection.
Also this week – news from the CDC that the type of mosquito that transmits the virus has spread further north in the United States. Federal health officials thought the Aedes aegypti mosquito was concentrated mostly in the south. But now, new maps show the insect’s range has broadened to the Midwest and as far north as New York City.
We learn more about this small but mighty vector in CuriosityStream’s new, original production — Viruses: Destruction and Creation.
Viruses: Destruction and Creation takes a closer look at these simple, but incredibly powerful organisms — that can sometimes be to our benefit, but oftentimes not.
Andrew Pekosz, PhD, is the director of the Center for Emerging Viruses and Infectious Diseases at the Johns Hopkins Bloomberg School of Public Health. In an interview with CuriosityStream Studios, he helped to explain the evolution of the virus and what makes it so powerful.
Dr. Pekosz: Stealth is one word that often comes in because a virus is able to find a cell, find a host. It’s able to get in and it’s able to cross-wire, disconnect, some of the alarm systems that a body has so that it can get a head start in terms of replicating itself and moving itself forward in terms of making enough copies of itself so it can spread to the next host. It can do a lot of this before a host even knows it’s infected. By the time you start responding and getting symptoms to an infection, oftentimes the virus is already well along its pathway of spreading to the next host and moving forward and propagating itself.
CuriosityStream: And how fast can that virus replicate?
Dr. Pekosz: A virus infected cell can make dozens, if not hundreds, of virus particles. From one infected cell you can easily get 20 infected cells. Each of those infected cells can then make another 20 infected cells. Before the host really has a way to respond to the infection with its immune system, you can have hundreds of thousands of cells, each of which are making hundreds and thousands of virus particles and that creates a huge bolus of viruses, in the case of Zika, in the blood, which now a mosquito coming to feed on that individual will pick up a blood meal that not just has the blood but also has the virus in it. That’s how the mosquito then becomes infected and can spread the infection on to other mosquitoes and, presumably, to other humans.
CuriosityStream: The Mosquito is the key here?
Dr. Pekosz: Mosquitoes are really fantastic little syringes… particularly female mosquitoes because it’s the female mosquitoes that need to bite and it’s the blood that the female mosquito ingests that she needs in order to lay an effective clutch of eggs. What a mosquito does is it not only bites but it also has to inject some of its saliva into that bite site in order to make sure that it can obtain a blood meal. Mosquitoes oftentimes bite several times before they actually will take their blood meal. Each time they bite they try to expel a little bit of saliva into that site to see if the blood will flow.
Where arboviruses have become exquisitely good at is finding ways to get into that saliva at very, very high concentrations. The virus has found a way to concentrate itself in that saliva so when the mosquito goes through its normal processes of trying to get a blood meal it inadvertently is introducing the virus into the host along with everything that it needs to try to pull that blood meal out. It is an incredibly effective way for the virus to replicate, get into a host, get multiple injections into a host, and start its process.
CuriosityStream: The National Institutes of Health has called the Zika outbreak an explosive pandemic that is truly remarkable.
Dr. Pekosz: Once Zika virus entered South America it seems to have just exploded in terms of the number of human cases. In an incredibly short period of time we’ve gone from Zika not being present in a continent to having close to a million cases, probably, of infection. That explosiveness and how quickly the virus has spread and caused so many infections is one of the main reasons why national public health agencies and the World Health Organization are so concerned about this spread.