What to Know about the Fast-Spreading Delta Variant
A highly contagious form of the coronavirus known as the Delta variant is spreading rapidly and becoming increasingly prevalent around the world. First identified in India in December, Delta has now been identified in 111 countries.
In the United States, the variant now accounts for 83% of sequenced COVID-19 cases, said Rochelle Walensky, director of the Centers for Disease Control and Prevention, at a July 20 Senate hearing. In May, Delta was responsible for just 3% of U.S. cases. The World Health Organization projects that Delta will become the dominant variant globally over the coming months.
So, how worried should you be about the Delta variant? We asked experts some common questions about Delta.
What is a variant?
To understand Delta, it's helpful to first understand what a variant is. When a virus infects a person, it gets into your cells and makes a copy of its genome so it can replicate and spread throughout your body.
In the process of making new copies of itself, the virus can make a mistake in its genetic code. Because viruses are replicating all the time, these mistakes â also called mutations â happen pretty often. A new variant emerges when a virus acquires one or more new mutations and starts spreading within a population.
There are thousands of SARS-CoV-2 variants, but most of them don't substantially change the way the virus behaves. The variants that scientists are most interested in are known as variants of concern. These are versions of the virus with mutations that allow the virus to spread more easily, evade vaccines, or cause more severe disease.
"The vast majority of the mutations that have accumulated in SARS-CoV-2 don't change the biology as far as we're concerned," said Jennifer Surtees, a biochemist at the University of Buffalo who's studying the coronavirus. "But there have been a handful of key mutations and combinations of mutations that have led to what we're now calling variants of concern."
One of those variants of concern is Delta, which is now driving many new COVID-19 infections.
Why is the Delta variant so concerning?
"The reason why the Delta variant is concerning is because it's causing an increase in transmission," said Alba Grifoni, an infectious disease researcher at the La Jolla Institute for Immunology. "The virus is spreading faster and people â particularly those who are not vaccinated yet â are more prone to exposure."
The Delta variant has a few key mutations that make it better at attaching to our cells and evading the neutralizing antibodies in our immune system. These mutations have changed the virus enough to make it more than twice as contagious as the original SARS-CoV-2 virus that emerged in Wuhan and about 50% more contagious than the Alpha variant, previously known as B.1.1.7, or the U.K. variant.
These mutations were previously seen in other variants on their own, but it's their combination that makes Delta so much more infectious.
Do vaccines work against the Delta variant?
The good news is, the COVID-19 vaccines made by AstraZeneca, Johnson & Johnson, Moderna, and Pfizer still work against the Delta variant. They remain more than 90% effective at preventing hospitalizations and death due to Delta. While they're slightly less protective against disease symptoms, they're still very effective at preventing severe illness caused by the Delta variant.
"They're not as good as they were against the prior strains, but they're holding up pretty well," said Eric Topol, a physician and director of the Scripps Translational Research Institute, during a July 19 briefing for journalists.
Because Delta is better at evading our immune systems, it's likely causing more breakthrough infections â COVID-19 cases in people who are vaccinated. However, breakthrough infections were expected before the Delta variant became widespread. No vaccine is 100% effective, so breakthrough infections can happen with other vaccines as well. Experts say the COVID-19 vaccines are still working as expected, even if breakthrough infections occur. The majority of these infections are asymptomatic or cause only mild symptoms.
Should vaccinated people worry about the Delta variant?
Vaccines train our immune systems to protect us against infection. They do this by spurring the production of antibodies, which stick around in our bodies to help fight off a particular pathogen in case we ever come into contact with it.
But even if the new Delta variant slips past our neutralizing antibodies, there's another component of our immune system that can help overtake the virus: T cells. Studies are showing that the COVID-19 vaccines also galvanize T cells, which help limit disease severity in people who have been vaccinated.
"While antibodies block the virus and prevent the virus from infecting cells, T cells are able to attack cells that have already been infected," Grifoni said. In other words, T cells can prevent the infection from spreading to more places in the body. A study published July 1 by Grifoni and her colleagues found that T cells were still able to recognize mutated forms of the virus â further evidence that our current vaccines are effective against Delta.
Can fully vaccinated people spread the Delta variant?
Previously, scientists believed it was unlikely for fully vaccinated individuals with asymptomatic infections to spread Covid-19. But the Delta variant causes the virus to make so many more copies of itself inside the body, and high viral loads have been found in the respiratory tracts of people who are fully vaccinated. This suggests that vaccinated people may be able to spread the Delta variant to some degree.
If you have COVID-19 symptoms, even if you're fully vaccinated, you should get tested and isolate from friends and family because you could spread the virus.
What risk does Delta pose to unvaccinated people?
The Delta variant is behind a surge in cases in communities with low vaccination rates, and unvaccinated Americans currently account for 97% of hospitalizations due to COVID-19, according to Walensky. The best thing you can do right now to prevent yourself from getting sick is to get vaccinated.
Gigi Gronvall, an immunologist and senior scholar at the Johns Hopkins Center for Health Security, said in this week's "Making Sense of Science" podcast that it's especially important to get all required doses of the vaccine in order to have the best protection against the Delta variant. "Even if it's been more than the allotted time that you were told to come back and get the second, there's no time like the present," she said.
With more than 3.6 billion COVID-19 doses administered globally, the vaccines have been shown to be incredibly safe. Serious adverse effects are rare, although scientists continue to monitor for them.
Being vaccinated also helps prevent the emergence of new and potentially more dangerous variants. Viruses need to infect people in order to replicate, and variants emerge because the virus continues to infect more people. More infections create more opportunities for the virus to acquire new mutations.
Surtees and others worry about a scenario in which a new variant emerges that's even more transmissible or resistant to vaccines. "This is our window of opportunity to try to get as many people vaccinated as possible and get people protected so that so that the virus doesn't evolve to be even better at infecting people," she said.
Does Delta cause more severe disease?
While hospitalizations and deaths from COVID-19 are increasing again, it's not yet clear whether Delta causes more severe illness than previous strains.
How can we protect unvaccinated children from the Delta variant?
With children 12 and under not yet eligible for the COVID-19 vaccine, kids are especially vulnerable to the Delta variant. One way to protect unvaccinated children is for parents and other close family members to get vaccinated.
It's also a good idea to keep masks handy when going out in public places. Due to risk Delta poses, the American Academy of Pediatrics issued new guidelines July 19 recommending that all staff and students over age 2 wear face masks in school this fall, even if they have been vaccinated.
Parents should also avoid taking their unvaccinated children to crowded, indoor locations and make sure their kids are practicing good hand-washing hygiene. For children younger than 2, limit visits with friends and family members who are unvaccinated or whose vaccination status is unknown and keep up social distancing practices while in public.
While there's no evidence yet that Delta increases disease severity in children, parents should be mindful that in some rare cases, kids can get a severe form of the disease.
"We're seeing more children getting sick and we're seeing some of them get very sick," Surtees said. "Those children can then pass on the virus to other individuals, including people who are immunocompromised or unvaccinated."
Breakthrough drones deliver breast milk in rural Uruguay
Until three months ago, nurse Leopoldina Castelli used to send bottles of breast milk to nourish babies in the remote areas of TacuarembĂł, in northern Uruguay, by way of ambulances or military trucks. That is, if the vehicles were available and the roads were passable, which wasnât always the case. Now, five days per week, she stands by a runway at the hospital, located in TacuarembĂłâs capital, watching a drone take off and disappear from view, carrying the milk to clinics that serve the babiesâ families.
The drones can fly as far as 62 miles. Long distances and rough roads are no obstacles. The babies, whose mothers struggle to produce sufficient milk and cannot afford formula, now receive ample supplies for healthy growth. âToday we provided nourishment to a significantly larger number of children, and this is something that deeply moves me,â Castelli says.
About two decades ago, the TacuarembĂł hospital established its own milk bank, supported by donations from mothers across TacuarembĂł. Over the years, the bank has provided milk to infants immediately after birth. It's helped drive a âsignificant and sustainedâ decrease in infant mortality, says the hospital director, Ciro Ferreira.
But these children need breast milk throughout their first six months, if not longer, to prevent malnutrition and other illnesses that are prevalent in rural TacuarembĂł. Ground transport isn't quick or reliable enough to meet this goal. It can take several hours, during which the milk may spoil due to a lack of refrigeration.
The battery-powered drones have been the difference-maker. The project to develop them, financed by the UNICEF Innovation Fund, is the first of its kind in Latin America. To Castelli, it's nothing short of a revolution. TacuarembĂł Hospital, along with three rural clinics in the most impoverished part of Uruguay, are its leaders.
"This marks the first occasion when the public health system has been directly impacted [by our technology]," says SebastiĂĄn MacĂas, the CEO and co-founder of Cielum, an engineer at the University Republic, which collaborated on the technology with a Uruguayan company called Cielum and a Swiss company, Rigitech.
The drone can achieve a top speed of up to 68 miles per hour, is capable of flying in light rain, and can withstand winds of up to 30 miles per hour at a maximum altitude of 120 meters.
"We have succeeded in embracing the mothers from rural areas who were previously slipping through the cracks of the system," says Ferreira, the hospital director. He envisions an expansion of the service so it can improve health for children in other rural areas.
Nurses load the drone for breast milk delivery.
SebastiĂĄn MacĂas - Cielum
The star aircraft
The drone, which costs approximately $70,000, was specifically designed for the transportation of biological materials. Constructed from carbon fiber, it's three meters wide, two meters long and weighs 42 pounds when fully loaded. Additionally, it is equipped with a ballistic parachute to ensure a safe descent in case the technology fails in midair. Furthermore, it can achieve a top speed of 68 miles per hour, fly in light rain, and withstand winds of 30 miles per hour at a height of 120 meters.
Inside, the drones feature three refrigerated compartments that maintain a stable temperature and adhere to the United Nationsâ standards for transporting perishable products. These compartments accommodate four gallons or 6.5 pounds of cargo. According to MacĂas, that's more than sufficient to carry a weekâs worth of milk for one infant on just two flights, or 3.3 pounds of blood samples collected in a rural clinic.
âFrom an energy perspective, it serves as an efficient mode of transportation and helps reduce the carbon emissions associated with using an ambulance,â said MacĂas. Plus, the ambulance can remain available in the town.
MacĂas, who has led software development for the drone, and three other technicians have been trained to operate it. They ensure that the drone stays on course, monitor weather conditions and implement emergency changes when needed. The software displays the in-flight positions of the drones in relation to other aircraft. All agricultural planes in the region receive notification about the drone's flight path, departure and arrival times, and current location.
The future: doubling the drone's reach
Forty-five days after its inaugural flight, the drone is now making five flights per week. It serves two routes: 34 miles to Curtina and 31 miles to Tambores. The drone reaches Curtina in 50 minutes while ambulances take double that time, partly due to the subpar road conditions. Pueblo Ansina, located 40 miles from the state capital, will soon be introduced as the third destination.
Overall, the droneâs schedule is expected to become much busier, with plans to accomplish 20 weekly flights by the end of October and over 30 in 2024. Given the droneâs speed, MacĂas is contemplating using it to transport cancer medications as well.
âWhen it comes to using drones to save lives, for us, the sky is not the limit," says Ciro Ferreira, TacuarembĂł hospital director.
In future trips to clinics in San Gregorio de Polanco and CaraguatĂĄ, the drone will be pushed to the limit. At these locations, a battery change will be necessary, but it's worth it. The route will cover up to 10 rural TacuarembĂł clinics plus one hospital outside TacuarembĂł, in Rivera, close to the border with Brazil. Currently, because of a shortage of ambulances, the delivery of pasteurized breast milk to Rivera only occurs every 15 days.
âThe expansion to Rivera will include 100,000 more inhabitants, doubling the healthcare reach,â said Ferreira, the director of the TacuarembĂł Hospital. In itself, Ferreira's hospital serves the medical needs of 500,000 people as one of the largest in Uruguay's interior.
Alejandro Del Estal, an aeronautical engineer at Rigitech, traveled from Europe to TacuarembĂł to oversee the construction of the vertiports â the defined areas that can support dronesâ take-off and landing â and the first flights. He pointed out that once the flight network between hospitals and rural polyclinics is complete in Uruguay, it will rank among the five most extensive drone routes in the world for any activity, including healthcare and commercial uses.
Cielum is already working on the long-term sustainability of the project. The aim is to have more drones operating in other rural regions in the western and northern parts of the country. The company has received inquiries from Argentina and Colombia, but, as MacĂas pointed out, they are exercising caution when making commitments. Expansion will depend on the development of each countryâs regulations for airspace use.
For Ferreira, the advantages in Uruguay are evident: "This approach enables us to bridge the geographical gap, enhance healthcare accessibility, and reduce the time required for diagnosing and treating rural inhabitants, all without the necessity of them traveling to the hospital,â he says. "When it comes to using drones to save lives, for us, the sky is not the limit."
After spaceflight record, NASA looks to protect astronauts on even longer trips
At T-minus six seconds, the main engines of the Atlantis Space Shuttle ignited, rattling its capsule âlike a skyscraper in an earthquake,â according to astronaut Tom Jones, describing the 1988 launch. As the rocket lifted off and accelerated to three times the force of Earth's gravity, âIt felt as if two of my friends were standing on my chest and wouldnât get off.â But when Atlantis reached orbit, the main engines cut off, and the astronauts were suddenly weightless.
Since 1961, NASA has sent hundreds of astronauts into space while working to making their voyages safer and smoother. Yet, challenges remain. Weightlessness may look amusing when watched from Earth, but it has myriad effects on cognition, movement and other functions. When missions to space stretch to six months or longer, microgravity can impact astronautsâ health and performance, making it more difficult to operate their spacecraft.
Yesterday, NASA astronaut Frank Rubio returned to Earth after over one year, the longest single spaceflight for a U.S. astronaut. But this is just the start; longer and more complex missions into deep space loom ahead, from returning to the moon in 2025 to eventually sending humans to Mars. To ensure that these missions succeed, NASA is increasing efforts to study the biological effects and prevent harm.
The dangers of microgravity are real
A NASA report published in 2016 details a long list of incidents and near-misses caused â at least partly â by space-induced changes in astronautsâ vision and coordination. These issues make it harder to move with precision and to judge distance and velocity.
According to the report, in 1997, a resupply ship collided with the Mir space station, possibly because a crew member bumped into the commander during the final docking maneuver. This mishap caused significant damage to the space station.
Returns to Earth suffered from problems, too. The same report notes that touchdown speeds during the first 100 space shuttle landings were âoutside acceptable limits. The fastest landing on record â 224 knots (258 miles) per hour â was linked to the commanderâs momentary spatial disorientation.â Earlier, each of the six Apollo crews that landed on the moon had difficulty recognizing moon landmarks and estimating distances. For example, Apollo 15 landed in an unplanned area, ultimately straddling the rim of a five-foot deep crater on the moon, harming one of its engines.
Spaceflight causes unique stresses on astronautsâ brains and central nervous systems. NASA is working to reduce these harmful effects.
NASA
Space messes up your brain
In space, astronauts face the challenges of microgravity, ionizing radiation, social isolation, high workloads, altered circadian rhythms, monotony, confined living quarters and a high-risk environment. Among these issues, microgravity is one of the most consequential in terms of physiological changes. It changes the brainâs structure and its functioning, which can hurt astronautsâ performance.
The brain shifts upwards within the skull, displacing the cerebrospinal fluid, which reduces the brainâs cushioning. Essentially, the brain becomes crowded inside the skull like a pair of too-tight shoes.
Thatâs partly because of how being in space alters blood flow. On Earth, gravity pulls our blood and other internal fluids toward our feet, but our circulatory valves ensure that the fluids are evenly distributed throughout the body. In space, thereâs not enough gravity to pull the fluids down, and they shift up, says Rachael D. Seidler, a physiologist specializing in spaceflight at the University of Florida and principal investigator on many space-related studies. The head swells and legs appear thinner, causing what astronauts call âpuffy face chicken legs.â
âThe brain changes at the structural and functional level,â says Steven Jillings, equilibrium and aerospace researcher at the University of Antwerp in Belgium. âThe brain shifts upwards within the skull,â displacing the cerebrospinal fluid, which reduces the brainâs cushioning. Essentially, the brain becomes crowded inside the skull like a pair of too-tight shoes. Some of the displaced cerebrospinal fluid goes into cavities within the brain, called ventricles, enlarging them. âThe remaining fluids pool near the chest and heart,â explains Jillings. After 12 consecutive months in space, one astronaut had a ventricle that was 25 percent larger than before the mission.
Some changes reverse themselves while others persist for a while. An example of a longer-lasting problem is spaceflight-induced neuro-ocular syndrome, which results in near-sightedness and pressure inside the skull. A study of approximately 300 astronauts shows near-sightedness affects about 60 percent of astronauts after long missions on the International Space Station (ISS) and more than 25 percent after spaceflights of only a few weeks.
Another long-term change could be the decreased ability of cerebrospinal fluid to clear waste products from the brain, Seidler says. Thatâs because compressing the brain also compresses its waste-removing glymphatic pathways, resulting in inflammation, vulnerability to injuries and worsening its overall health.
The effects of long space missions were best demonstrated on astronaut twins Scott and Mark Kelly. This NASA Twins Study showed multiple, perhaps permanent, changes in Scott after his 340-day mission aboard the ISS, compared to Mark, who remained on Earth. The differences included declines in Scottâs speed, accuracy and cognitive abilities that persisted longer than six months after returning to Earth in March 2016.
By the end of 2020, Scottâs cognitive abilities improved, but structural and physiological changes to his eyes still remained, he said in a BBC interview.
âIt seems clear that the upward shift of the brain and compression of the surrounding tissues with ventricular expansion might not be a good thing,â Seidler says. âBut, at this point, the long-term consequences to brain health and human performance are not really known.â
NASA astronaut Kate Rubins conducts a session for the Neuromapping investigation.
NASA
Staying sharp in space
To investigate how prolonged space travel affects the brain, NASA launched a new initiative called the Complement of Integrated Protocols for Human Exploration Research (CIPHER). âCIPHER investigates how long-duration spaceflight affects both brain structure and function,â says neurobehavioral scientist Mathias Basner at the University of Pennsylvania, a principal investigator for several NASA studies. âThrough it, we can find out how the brain adapts to the spaceflight environment and how certain brain regions (behave) differently after â relative to before â the mission.â
To do this, he says, âAstronauts will perform NASAâs cognition test battery before, during and after six- to 12-month missions, and will also perform the same test battery in an MRI scanner before and after the mission. We have to make sure we better understand the functional consequences of spaceflight on the human brain before we can send humans safely to the moon and, especially, to Mars.â
As we go deeper into space, astronauts cognitive and physical functions will be even more important. âA trip to Mars will take about one yearâŚand will introduce long communication delays,â Seidler says. âIf you are on that mission and have a problem, it may take eight to 10 minutes for your message to reach mission control, and another eight to 10 minutes for the response to get back to you.â In an emergency situation, that may be too late for the response to matter.
âOn a mission to Mars, astronauts will be exposed to stressors for unprecedented amounts of time,â Basner says. To counter them, NASA is considering the continuous use of artificial gravity during the journey, and Seidler is studying whether artificial gravity can reduce the harmful effects of microgravity. Some scientists are looking at precision brain stimulation as a way to improve memory and reduce anxiety due to prolonged exposure to radiation in space.
Other scientists are exploring how to protect neural stem cells (which create brain cells) from radiation damage, developing drugs to repair damaged brain cells and protect cells from radiation.
To boldly go where no astronauts have gone before, they must have optimal reflexes, vision and decision-making. In the era of deep space exploration, the brainâwithout a doubtâis the final frontier.
Additionally, NASA is scrutinizing each aspect of the mission, including astronaut exercise, nutrition and intellectual engagement. âWe need to give astronauts meaningful work. We need to stimulate their sensory, cognitive and other systems appropriately,â Basner says, especially given their extreme confinement and isolation. The scientific experiments performed on the ISS â like studying how microgravity affects the ability of tissue to regenerate is a good example.
âWe need to keep them engaged socially, too,â he continues. The ISS crew, for example, regularly broadcasts from space and answers prerecorded questions from students on Earth, and can engage with social media in real time. And, despite tight quarters, NASA is ensuring the crew capsule and living quarters on the moon or Mars include private space, which is critical for good mental health.
Exploring deep space builds on a foundation that began when astronauts first left the planet. With each mission, scientists learn more about spaceflight effects on astronautsâ bodies. NASA will be using these lessons to succeed with its plans to build science stations on the moon and, eventually, Mars.
âThrough internally and externally led research, investigations implemented in space and in spaceflight simulations on Earth, we are striving to reduce the likelihood and potential impacts of neurostructural changes in future, extended spaceflight,â summarizes NASA scientist Alexandra Whitmire. To boldly go where no astronauts have gone before, they must have optimal reflexes, vision and decision-making. In the era of deep space exploration, the brainâwithout a doubtâis the final frontier.