Tag Archives: airborne

Archaeologists uncover hidden citadel in ancient Maya city

Using airborne data, a group of archaeologists discovered a previously unknown structural complex near the Maya city of Tikal, in what is now Guatemala. While the city is notable in itself, what makes the discovery even more interesting is that the complex’s structures are similar to buildings in Teotihuacan, a Mesoamerican city. 

View of the Teotihuacan Complex at Tikal. Image credit: Researchers

The ruins of Tikal have been the subject of extensive study since the 1950s, with researchers documenting details of every structure and cataloguing all excavated items. This has made Tikal one of the best understood archeological sites in the world. Nevertheless, there’s always something new to discover — as we can see in this study. 

Stephen Houston from Brown University and Thomas Garrison from the University of Texas have discovered that what was thought to be a natural hilly area near Tikal’s center was actually a neighborhood of ruined buildings intentionally designed to look like Teotihuacan, the most powerful and largest city there was in ancient Americas.

“What we had taken to be natural hills actually were shown to be modified and conformed to the shape of the citadel,” Houston said in a statement. “Regardless of who built this smaller-scale replica and why, it shows without a doubt that there was a different level of interaction between Tikal and Teotihuacan than previously believed.”

Understanding Tikal

The area where the complex was found hadn’t been explored until now as researchers believed that the hills were just part of the natural landscape. Houston and Garrison used LIDAR, a light detection and ranging technology, to build 3D models of the surface and identify structural features. This was followed then by an on-site exploration that confirmed the findings.

In the area, which is roughly 62 acres, the researchers confirmed with excavations that the buildings were built with mud plaster than limestone, a material usually used by the Maya society. In fact, the structures appeared to be scaled-down versions of the buildings from Teotihuacan’s citadel, located more than 1,000 kilometers (621 miles) away. 

The researchers also found human remains near the replicated buildings. The bodies were surrounded by several funerary items such as animal bones and projectile points. There was also plenty of coal, suggesting the assemblage was deliberately set on fire – a death ritual that is similar to the one used with warriors at the citadel of Teotihuacan. 

It’s not the first-time evidence is found of the influence of Teotihuacan in Tikal, as contacts between the two societies were common. Maya elites lived and traded in Teotihuacan. But after centuries of peace, Teotihuacan conquered Tikal in 378 CE.  The new findings suggest a more intense contact between the two, the researchers argue.

“The architectural complex we found very much appears to have been built for people from Teotihuacan or those under their control,” Houston said. “Perhaps it was something like an embassy complex, but when we combine previous research with our latest findings, it suggests something more heavy-handed, like occupation or surveillance.”

The study was published in the journal Antiquity. 

It’s time to face the fact that the coronavirus is airborne

In the first weeks of the pandemic, the word ‘droplets’ seemed ubiquitous. It spreads through droplets. It’s the droplets that pass a virus. There’s a difference between droplet and airborne transmission and the initial trials seemed to suggest that we were dealing with the former, not the latter.

But recent studies are starting to tell a different story.

Image credits: James Gathany.

What airborne means

The current scientific consensus is that SARS-CoV-2, the novel coronavirus causing a pandemic, is mostly spread through droplets: tiny globs of mucus or saliva propelled from people’s noses or mouth when they cough, sneeze, or even just talk.

When droplets become really small (diameter of 5μm or less) and become suspended in the air, they’re called aerosols — and this is a key difference. Due to their small size, aerosols can stay suspended for longer periods of time (even a few hours) and can travel further than large droplets.

A virus that can spread via aerosols (like measles, for instance) is considered airborne, while SARS-CoV-2 is not airborne — or so we thought, initially. More and more, studies are starting to suggest that airborne transmission could be a possibility.

For instance, one recent study used laser light scattering to detect droplets as people talked, finding that droplets as small as 4μm were produced. This information, coupled with another study that found that small droplets can remain infectious for up to 16 hours, seems to back the idea of airborne transmission. However, the World Health Organization argued that this doesn’t “reflect normal human cough conditions”.

The airborne debate remained suspended in the air, until studies actually found coronavirus suspended in the air.

A smoking gun

An estimation of infection risks under various circumstances. Credits: Morawska et al (2020).

Studies pointing at airborne transmission were already starting to add up; one such study in Wuhan, where the pandemic emerged, found coronavirus genetic material in samples from two hospitals, but it wasn’t clear if the virus was still infectious. In another study from China, families eating at a restaurant all became infected despite having no contact with each other and staying several meters apart.

But a smoking gun was missing, until recently.

In a new study, researchers have found evidence of SARS-CoV-2 suspended airborne in a hospital room with COVID-19 patients. The virus was still active, as researchers managed to culture it from air samples. Although the study has not yet been peer-reviewed, this is a clear smoking gun, says Linsey Marr, an expert in airborne spread of viruses who was not involved in the work. In a separate Tweet, Marr also said the WHO is still in denial about airborne transmission.

After a growing mass of studies hinted at airborne transmission, 239 scientists published a commentary in Clinical Infectious Diseases calling for the recognition of airborne transmission for COVID-19.

What does this mean?

By now, airborne transmission seems more than just a possibility — it’s happening. We still don’t know how often it happens or how important the role of airborne transmission is for the pandemic. But here’s the thing: the airborne/droplet difference is not a fixed line where it’s either one or another. A sneeze or cough (or even just speech) can create a swarm of droplets in many different size ranges, some of which could remain suspended in the air for a longer period of time.

The problem is that figuring out what size of droplets causes most of the disease transmission is an extremely challenging task. Basically, it could be a long time before we figure out just how important airborne transmission is in this case.

“Even for the flu, which we’ve studied for decades, we still don’t know how much is transmitted by aerosols or by touching contaminated objects,” Marr says.

For our day to day life, this suggests that social distancing alone might not be enough to stop the spread of disease. Whether it’s one meter, 2 meters, or 6 feet, most nations made some recommendation giving people a sense of security if they are beyond a specific distance — that sense might not be fully warranted. The findings also push for more precautions regarding ventilation.

The virus seems to spread through air. We don’t know how often it happens, but it’s one more thing we need to consider and adjust accordingly.

Kawasaki disease origin finally traced (probably)

The Kawasaki disease, a strange and highly dangerous disease first identified in Japan has been traced to the croplands in China.

If the study’s conclusions are correct, than the Kawasaki disease may be the first condition known to spread by a wind-borne toxin. Credits: Christian Kober/Robert Harding World Imagery/Corbis

Also called lymph node syndrome, the Kawasaki disease is an autoimmune disease largely seen in children under five years of age in which the medium-sized blood vessels throughout the body become inflamed. To oversimplify it, the body starts to attack its own blood vessels, which can have dramatic and potentially fatal consequences (even after a few years without any symptoms). Kawasaki disease can only be diagnosed clinically (i.e. by medical signs and symptoms). There exists no specific laboratory test for this condition – therefore, the condition is often times extremely difficult to diagnose.

The pathogens responsible for the disease enter through mucous membranes and work their way into the arteries – and while it has been previously suggested that the disease may be carried by wind from far away, its origins still remained unknown. Now, researchers believe they have finally pinpointed the location to the vast farmlands of northeastern China where maize (corn), rice and wheat are grown.

In order to reach this conclusion, the team analysed infection records for Japan during the epidemics of 1979, 1982, and 1986 as well as more recent seasonal outbreaks. They analyzed the wind patterns and speed for those periods, and ultimately calculated the likely incubation time for the disease — 6 hours to 2.5 days, but probably less than 24 hours.

They reached these figures after comparing the arrival time of winds from the source region in China with the timing of the first diagnosed cases during various epidemics. Initially, this was actually pretty misleading, so they also went for a different approach.

Previous data had already shown a significant correlation between Kawasaki disease and tropospheric wind patterns; winds blowing from central Asia correlate with Kawasaki disease cases in Japan, Hawaii and San Diego, but since even the cause(s) of the disease remained unknown, researchers were hesitant to draw any clear conclusions about its origin.


“The incubation time suggests we should be looking in a very different direction,” says study co-author Jane Burns, a paediatrics researcher at the University of California, San Diego

They suspected that the disease is carried by a bacteria or fungus, and they analyzed what kind of particles the winds from China were carrying. Indeed, they found a remarkably high concentration of the fungus Candida.

“I think there is evidence that [Kawasaki disease] looks like other bacterial toxin diseases,” says Samuel Dominguez, a pediatric infectious-disease specialist at the University of Colorado School of Medicine in Aurora.

So, as we demonstrated in a previous article, correlation does not imply causality – the Candida fungus may be irrelevant for the Kawasaki disease, it may have a tangential effect, it may be the partial or full cause of the disease – but so far, this is the best clue to the disease we have so far, so we’ll definitely be seeing some more research in this direction.

Scientific Reference: Rodó, X. et al. Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1400380111 (2014).