Syria-bound Russian military jet crashes with 92 onboard

Jun 9: The World Health Organization says it still believes the spread of the coronavirus from people without symptoms is “rare,” despite warnings from numerous experts worldwide that such transmission is more frequent and likely explains why the pandemic has been so hard to contain.

Maria Van Kerkhove, WHO''s technical lead on COVID-19 said at a press briefing on Monday that many countries are reporting cases of spread from people who are asymptomatic, or those with no clinical symptoms.

But when questioned in more detail about these cases, Van Kerkhove said many of them turn out to have mild disease, or unusual symptoms.

Although health officials in countries including Britain, the U.S. and elsewhere have warned that COVID-19 is spreading from people without symptoms, WHO has maintained that this type of spread is not a driver of the pandemic and is probably accounts for about 6 per cent of spread, at most.

Numerous studies have suggested that the virus is spreading from people without symptoms, but many of those are either anecdotal reports or based on modeling.

Van Kerkhove said that based on data from countries, when people with no symptoms of COVID-19 are tracked over a long period to see if they spread the disease, there are very few cases of spread.

“We are constantly looking at this data and we''re trying to get more information from countries to truly answer this question,” she said. “It still appears to be rare that asymptomatic individuals actually transmit onward.”

Kabul, Jan 27: A passenger plane crashed on Monday in a Taliban-held area of Afghanistan's Ghazni province, local officials said.

Arif Noori, spokesman for the provincial governor, said the plane went down around 1:10 p.m. local time in Deh Yak district, which is held by the Taliban. Two provincial council members also confirmed the crash.

The number of people on board and their fate was not immediately known, nor was the cause of the crash.

Ariana Airlines, Afghanistan's national carrier, dismissed the claim that one of their planes had crashed in a statement on their website, saying all their aircraft were operational and safe.

The mountainous Ghazni province sits in the foothills of the Hindu Kush mountains and is bitterly cold in winter.

The last major commercial air crash in Afghanistan occurred in 2005 when a Kam Air flight from western Herat to the capital Kabul crashed into the mountains as it tried to land in snowy weather.

The war however has seen a number of deadly crashes of military aircraft. One of the most spectacular occurred in 2013 when an American Boeing 747 cargo jet crashed shortly after takeoff from Bagram air base north of Kabul en route to Dubai in the United Arab Emirates. All seven crew member were killed.

Afghanistan's aviation industry suffered desperately during the rule of the Taliban when its only airline Ariana was subject to punishing sanctions and allowed to fly only to Saudi Arabia for Hajj flights.

Since the overthrow of the religious regime smaller private airlines have emerged but the industry is still a nascent one.

London, May 20: The current physical distancing guidelines of 6 feet may be insufficient to prevent COVID-19 transmission, according to a study which says a mild cough in low wind speeds can propel saliva droplets by as much as 18 feet.

Researchers, including those from the University of Nicosia in Cyprus, said a good baseline for studying the airborne transmission of viruses, like the one behind the COVID-19 pandemic, is a deeper understanding of how particles travel through the air when people cough.

In the study, published in the journal Physics of Fluids, they said even with a slight breeze of about four kilometres per hour (kph), saliva travels 18 feet in 5 seconds.

"The droplet cloud will affect both adults and children of different heights," said study co-author Dimitris Drikakis from the University of Nicosia.

According to the scientists, shorter adults and children could be at higher risk if they are located within the trajectory of the saliva droplets.

They said saliva is a complex fluid, which travels suspended in a bulk of surrounding air released by a cough, adding that many factors affect how saliva droplets travel in the air.

These factors, the study noted, include the size and number of droplets, how they interact with one another and the surrounding air as they disperse and evaporate, how heat and mass are transferred, and the humidity and temperature of the surrounding air.

In the study, the scientists created a computer simulation to examine the state of every saliva droplet moving through the air in front of a coughing person.

The model considered the effects of humidity, dispersion force, interactions of molecules of saliva and air, and how the droplets change from liquid to vapour and evaporate, along with a grid representing the space in front of a coughing person.

Each grid, the scientists said, holds information about variables like pressure, fluid velocity, temperature, droplet mass, and droplet position.

The study analysed the fates of nearly 1,008 simulated saliva droplets, and solved as many as 3.7 million equations.

"The purpose of the mathematical modelling and simulation is to take into account all the real coupling or interaction mechanisms that may take place between the main bulk fluid flow and the saliva droplets, and between the saliva droplets themselves," explained Talib Dbouk, another co-author of the study.

However, the researchers added that further studies are needed to determine the effect of ground surface temperature on the behaviour of saliva in air.

They also believe that indoor environments, especially ones with air conditioning, may significantly affect the particle movement through air.

This work is important since it concerns safety distance guidelines, and advances the understanding of the transmission of airborne diseases, Drikakis said.