WHO acknowledges 'emerging evidence' of airborne spread of Covid-19

The World Health Organisation on Tuesday acknowledged "emerging evidence" of the airborne spread of the novel coronavirus, after a group of scientists urged the global body to update its guidance on how the respiratory disease is spread.

Speaking at a briefing in Geneva, WHO expert Benedetta Allegranzi said the organization believed it had "been open to the evidence on modes of transmission" of the new virus.

Coronavirus across the globe
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Coronavirus across the globe
A girl hugs her sister as she cries before they leave the Palestinian Rafah border crossing with Egypt, which was reopened for the first time since it was closed in March due to concerns about the spread of the coronavirus disease (COVID-19), in the southern Gaza Strip August 12, 2020. REUTERS/Mohammed Salem TPX IMAGES OF THE DAY
MUMBAI, INDIA - AUGUST 13: Healthcare staff check the temperature and pulse rate of the residents of Kurar Village at Malad(E) during Covid-19 pandemic, on August 13, 2020 in Mumbai, India. (Photo by Satyabrata Tripathy/Hindustan Times via Getty Images)
Mauricio Castiblanco, a Catholic deacon wearing protective gear, conducts a farewell ceremony for a deceased person outside the Chapinero cemetery, amidst an outbreak of the coronavirus disease (COVID-19), in Bogota, Colombia August 10, 2020. Picture taken August 10, 2020. REUTERS/Luisa Gonzalez
Catholic Priest Omar is pictured as Military members work on disinfection of the Christ the Redeemer statue ahead of its re-opening amid the coronavirus disease (COVID-19) outbreak, in Rio de Janeiro, Brazil, August 13, 2020. REUTERS/Ricardo Moraes TPX IMAGES OF THE DAY
14 August 2020, Saxony, Görlitz: General practitioner Klaus Heckelmann (l) takes a smear from a traveller. Together with the Malteser and the Association of Statutory Health Insurance Physicians, travel returnees should be able to be tested for the corona virus in Saxony. Photo: Daniel Schäfer/dpa-Zentralbild/Daniel Schäfer (Photo by Daniel Schäfer/picture alliance via Getty Images)
Medical personnel carries an oxygen cylinder at the entrance door of the COVID-19 area of the Moscoso Puello Hospital in Santo Domingo on August 13, 2020 amid the novel coronavirus pandemic. - The Dominican Republic reports 83,134 infections from COVID-19 and 1,393 deaths so far, according to the National Public Health Service. (Photo by Erika SANTELICES / AFP) (Photo by ERIKA SANTELICES/afp/AFP via Getty Images)
LISBON, PORTUGAL - AUGUST 13: Amadou Haidara of RB Leipzig arrives at the stadium prior to the UEFA Champions League Quarter Final match between RB Leipzig and Club Atletico de Madrid at Estadio Jose Alvalade on August 13, 2020 in Lisbon, Portugal. (Photo by Julian Finney - UEFA/UEFA via Getty Images)
PARIS, FRANCE - AUGUST 13: People wear masks in touristic and frequented areas of Paris as government takes new measures against coronavirus (Covid-19) forcing the wearing of mask in certain streets frequented in order to combat the pandemic in Paris, France on August 13, 2020. (Photo by Julien Mattia/Anadolu Agency via Getty Images)
DHAKA, Aug. 12, 2020 -- A woman works at a garment factory in Dhaka, Bangladesh, on Aug. 12, 2020. Bangladesh's July export income was over 44 percent higher than that in June, meaning the country's export sector is limping back to normalcy after suffering serious blows owing to COVID-19 impacts. Of the total earnings, the Export Promotion Bureau data showed the country's income from ready-made garment items, including knitwear and woven, stood at 3.24 billion U.S. dollars. (Xinhua via Getty) (Xinhua/Salim via Getty Images)
A runner removes her protective face mask at the start of the "Tour du Pays de Vaud" running stage race organised with health measures amid the COVID-19 outbreak, caused by the novel coronavirus, on August 12, 2020 in Champvent. - Switzerland announced on August 12, 2020 that with COVID-19 cases rising again, it was prolonging the ban on gatherings of more than 1,000 people until October 1, triggering upheaval for major sports. (Photo by Fabrice COFFRINI / AFP) (Photo by FABRICE COFFRINI/AFP via Getty Images)
NEW YORK, NEW YORK - AUGUST 12: Members of the NYPD Counterterrorism Bureau patrol Union Square while wearing face masks during the fourth phase of the coronavirus reopening on August 12, 2020 in New York, New York. The fourth phase allows outdoor arts and entertainment, sporting events without fans and media production. (Photo by Roy Rochlin/Getty Images)
People wearing face masks as a preventive measure against the COVID-19 coronavirus queue to get on a bus in Jakarta on August 13, 2020. (Photo by ADEK BERRY / AFP) (Photo by ADEK BERRY/AFP via Getty Images)
12 August 2020, North Rhine-Westphalia, Münster: A pupil of class 8a of the comprehensive school in Münster, wearing a mouth and nose mask, stands in front of a blackboard and solves an arithmetic problem. After the summer holidays, the federal state of North Rhine-Westphalia will start regular school operations again with compulsory masks. Photo: Guido Kirchner/dpa (Photo by Guido Kirchner/picture alliance via Getty Images)
YOGYAKARTA, INDONESIA - AUGUST 12: A bride, Sri Mujilestari, wear a transparant protective masks attend a mass wedding ceremony to commemorate the 75th Indonesia's National Independence Day at Cemara Sewu beach amid the Coronavirus pandemic on August 12, 2020 in Yogyakarta, Indonesia. Indonesia became an independent nation on 17th August 1945, having previously been under Dutch rule. Indonesia is struggling to contain hundreds of new daily cases of coronavirus amid easing of rules to allow economic activity to resume, and has reported more than 100,000 coronavirus cases and with at least more 5,900 recorded fatalities. (Photo by Ulet Ifansasti/Getty Images)
RAFAH, GAZA - AUGUST 11: Security forces wearing protective gear amid the new coronavirus pandemic are seen as as Palestinians begin crossing the border after Egypt opened the Rafah crossing with the Gaza Strip for three days, in Rafah, Gaza on August 11, 2020. The terminal will remain open in both directions to allow Palestinian travelers to leave and those stranded to return to Gaza, the embassy said in a statement. (Photo by Mustafa Hassona/Anadolu Agency via Getty Images)
Students with face masks line up on the schoolyard of the Petri primary school in Dortmund, western Germany, on August 12, 2020, amid the novel coronavirus COVID-19 pandemic. - Schools in the western federal state of North Rhine-Westphalia re-started under strict health guidelines after the summer holidays. (Photo by Ina FASSBENDER / AFP) (Photo by INA FASSBENDER/AFP via Getty Images)
NOIDA, INDIA - AUGUST 11: A health worker registers people for coronavirus testing, at Sector 30 District Hospital, on August 11, 2020 in Noida, India. (Photo by Sunil Ghosh/Hindustan Times via Getty Images)
Employees explain their work at the Bio Farma Pharmacy that produces vaccines for COVID-19 coronavirus in Bandung, West Java on August 12, 2020. - Indonesia on August 11 launched human trials of a Chinese-made coronavirus vaccine with some 1,600 volunteers slated to take part in the six-month study. (Photo by Bay ISMOYO / AFP) / The erroneous mention[s] appearing in the metadata of this photo by Bay ISMOYO has been modified in AFP systems in the following manner: adds [which will produce the vaccine early next year with a production capacity of 250 million vaccines a year]. Please immediately remove the erroneous mention[s] from all your online services and delete it (them) from your servers. If you have been authorized by AFP to distribute it (them) to third parties, please ensure that the same actions are carried out by them. Failure to promptly comply with these instructions will entail liability on your part for any continued or post notification usage. Therefore we thank you very much for all your attention and prompt action. We are sorry for the inconvenience this notification may cause and remain at your disposal for any further information you may require. (Photo by BAY ISMOYO/AFP via Getty Images)
SAINT CHRISTO EN JAREZ, FRANCE - AUGUST 12: Start / Primoz Roglic of Slovenia, Tom Dumoulin of The Netherlands, Robert Gesink of The Netherlands, Steven Kruijswijk of The Netherlands, Sepp Kuss of The United States, Tony Martin of Germany and Wout Van Aert of Belgium and Team Jumbo - Visma / Covid safety measures / Team Presentation / during the 72nd Criterium du Dauphine 2020, Stage 1 a 218,5km stage from Clermont Ferrand to Saint Christo en Jarez 752m / @dauphine / #Dauphiné / on August 12, 2020 in Saint Christo en Jarez, France. (Photo by Justin Setterfield/Getty Images)
A girl clad in mask poses for a picture during an awareness session about COVID-19 coronavirus disease held by a local kindergarten in Gaza City on August 10, 2020, as education facilities in the Palestinian enclave re-opened for the new 2020-2021 academic year following an easing of pandemic restrictions. (Photo by Mohammed ABED / AFP) (Photo by MOHAMMED ABED/AFP via Getty Images)
SURABAYA, INDONESIA - AUGUST 10, 2020 : Two child nutrition officers from the Surabaya City Public Health Center checked the growth and development and nutrition of children in densely populated areas in Surabaya, East Java province, Indonesia on August 10, 2020. In the conditions of the Covid-19 Pandemic, nutrition officers carry out checks by visiting the child's parents' house directly.- PHOTOGRAPH BY Budiono / Sijori images/ Barcroft Studios / Future Publishing (Photo credit should read Budiono,/ Sijori images/Barcroft Media via Getty Images)
10 August 2020, Mecklenburg-Western Pomerania, Binz: Bathers have settled on the Baltic beach in front of the pier. However, day tourists are still not allowed to travel to the federal state. Photo: Stefan Sauer/dpa (Photo by Stefan Sauer/picture alliance via Getty Images)
A health worker waits in front of a makeshift drive-through COVID-19 coronavirus testing booth in New Delhi on August 10, 2020. (Photo by Prakash SINGH / AFP) (Photo by PRAKASH SINGH/AFP via Getty Images)
People dance and attend a rave party, on an agricultural land in Causse Mejean, in the heart of the Cevennes National Park, southern France on August 10, 2020, despite the limitation of gatherings linked to COVID-19, the novel coronavirus. - The rally gathered up to 10,000 people announced the prefecture of Lozere. Starting from August 9, 2020 at 8:00 am, the gendarmes had blocked the access to prevent other people from joining the party where there were also very young children, according to the prefect. Two Covid-19 screening centers are being set up in transit areas, near the site, to be operational on Tuesday morning, also said Ms. Hatsch. (Photo by Pascal GUYOT / AFP) (Photo by PASCAL GUYOT/AFP via Getty Images)
ABU DHABI, UNITED ARAB EMIRATES - AUGUST 10: A man is tested using Laser-based DPI technology at a testing center at the Dubai-Abu Dhabi border on August 10, 2020 in Abu Dhabi, United Arab Emirates. The UAE has recorded around 62,000 cases of covid-19, with 357 deaths, among its population of 9.6 million people. New cases have steadily declined since a spike at the beginning of July. (Photo by Francois Nel/Getty Images)
BERLIN, GERMANY - AUGUST 09: Artists, performers and stage technicians demonstrate against insufficient government financial support as the coronavirus (COVID-19) pandemic continues on August 09, 2020 in Berlin, Germany. The protesters are calling for more monetary assistance to those who have not been able to perform due to health restrictions against public gatherings. (Photo by Adam Berry/Getty Images)
BERLIN, GERMANY - AUGUST 09: A drag queen joins artists, performers and stage technicians demonstrating against insufficient government financial support as the coronavirus (COVID-19) pandemic continues on August 09, 2020 in Berlin, Germany. The protesters are calling for more monetary assistance to those who have not been able to perform due to health restrictions against public gatherings. (Photo by Adam Berry/Getty Images)
An Iranian woman wearinga face shield walks along a street in the capital Tehran amid the novel coronavirus pandemic on August 9, 2020. (Photo by ATTA KENARE / AFP) (Photo by ATTA KENARE/AFP via Getty Images)
RIO DE JANEIRO, BRAZIL - AUGUST 09: The Archbishop of the City of Rio de Janeiro Dom Orani João Tempesta celebrates Mass in honor of the victims of coronavirus (COVID-19) and the families who lost parents and relatives in the pandemic at the Christ the Redeemer statue ,on August 9, 2020 in Rio de Janeiro, Brazil. Brazil has reached a milestone of more than 3 million coronavirus cases and 10.000 deaths. (Photo by Andre Coelho/Getty Images)
Interns and resident doctors attend a rally against the government medical policy in Seoul, South Korea, Friday, Aug. 7, 2020. Thousands of young doctors in South Korea began a strike Friday in protest of government medical policy, causing concerns about treatment of patients amid the coronavirus pandemic. (AP Photo/Ahn Young-joon)
Delegates wearing a protective face masks to help curb the spread of the coronavirus, attend on the first day of the Afghan Loya Jirga meeting in Kabul, Afghanistan, Friday, Aug. 7, 2020. The traditional council opened Friday in the Afghan capital to decide the release of a final 400 Taliban - the final hurdle to the start of negotiations between Kabul's leadership and the Taliban in keeping with a peace deal the United States signed with the insurgent movement in February. (AP Photo/Rahmat Gul)
TANGERANG, INDONESIA - AUGUST 7, 2020 : A worker sprays disinfectant to store held by shopping centre management after two of its employees tested positive for COVID-19 at shopping centre AEON Mall BSD City in Tangerang, Banten, Indonesia. August 7, 2020. Authorities conducts disinfection the facility and conduct rapid tests on 1,200 of the mall's employees and tenants. The COVID-19 cases in Indonesia rose by 2,473 within one day to 121,226, with the death toll adding by 72 to 5,593, the Health Ministry said on Friday. (JEFTA IMAGES)- PHOTOGRAPH BY Jefta Images / Barcroft Studios / Future Publishing (Photo credit should read Jefta Images/Barcroft Media via Getty Images)
NEW DELHI, INDIA - AUGUST 6: Blood samples collected during a serological survey at Ramjas School at Darya Ganj, on August 6, 2020 in New Delhi, India. (Photo by Vipin Kumar/Hindustan Times via Getty Images)
06 August 2020, Baden-Wuerttemberg, Stuttgart: One participant holds a sign in front of a motor home during a demonstration on the prohibition of sex workers from working during the Corona pandemic, saying "Sex work is real work". Since July 19, the city of Stuttgart has declared a complete ban on prostitution. Photo: Sebastian Gollnow/dpa (Photo by Sebastian Gollnow/picture alliance via Getty Images)
06 August 2020, Mecklenburg-Western Pomerania, Sellin: Tourists walk on the pier at the beach of Sellin on the island of Rügen. Day tourists, however, are not allowed to travel further into the federal state. Photo: Stefan Sauer/dpa-Zentralbild/dpa (Photo by Stefan Sauer/picture alliance via Getty Images)
A health worker performs a COVID19 swab test at a gymnasium in Navotas city, Philippines on Thursday, Aug. 6, 2020. The capital and outlying provinces returned to another lockdown after medical groups warned that the country was waging a losing battle against the coronavirus amid an alarming surge in infections. (AP Photo/Aaron Favila)
Health workers check residents at a free COVID19 swab testing at a gymnasium in Navotas city, Philippines, on Thursday, Aug. 6, 2020. The capital and outlying provinces returned to another lockdown after medical groups warned that the country was waging a losing battle against the coronavirus amid an alarming surge in infections. (AP Photo/Aaron Favila)
Catholic priest Fr. Hans Magdurulang blesses the COVID19 swab test area of a hospital in Manila, Philippines on Thursday, Aug. 6, 2020. The capital and outlying provinces returned to another lockdown after medical groups warned that the country was waging a losing battle against the coronavirus amid an alarming surge in infections. (AP Photo/Aaron Favila)
Wearing masks to prevent the spread of COVID19, elementary school students wait for classes to begin in Godley, Texas, Wednesday, Aug. 5, 2020. Three rural school districts in Johnson County were among the first in Texas to head back to school for in person classes for students. (AP Photo/LM Otero)
Victorian protective service officers are seen walking on patrol past a sign to urge people to stay home as lockdown of Melbourne forces people to stay at home if not working due to the continuing spread of COVID-19, Wednesday, Aug. 5, 2020. Victoria state, Australia's coronavirus hot spot, announced on Monday that businesses will be closed and scaled down in a bid to curb the spread of the virus. (AP Photo/Asanka Brendon Ratnayake)
Artists give finishing touches to a mural depicting frontline workers during a day-long complete lockdown imposed by the state government against the surge in COVID-19 coronavirus cases in Kolkata on August 5, 2020. (Photo by Dibyangshu SARKAR / AFP) (Photo by DIBYANGSHU SARKAR/AFP via Getty Images)
An activist of Rashtriya Bajrang Dal participates in a ceremony to mark the groundbreaking ceremony of a temple dedicated to the Hindu god Ram in Ayodhya, and the first anniversary of India's decision to revoke article 370, in Jammu, India, Wednesday, Aug 5, 2020. Despite the coronavirus restricting a large crowd, Hindus rejoiced as Indian Prime Minister Narendra Modi broke ground Wednesday on a long-awaited temple of their most revered god Ram at the site of a demolished 16th century mosque. Modi offered prayers to nine stone blocks with lord Ram inscribed on it amid chanting of Hindu religious hymns to symbolize the start of construction of the temple, which is expected to take three and a half years. (AP Photo/Channi Anand)
Jammu Kashmir policemen watch as local activists of India's ruling Bharatiya Janata Party (BJP) hoist the Indian National flag as they mark the first anniversary of India’s decision to revoke the disputed region’s semi-autonomy, in Srinagar, Indian controlled Kashmir, Wednesday, Aug. 5, 2020. India’s Hindu-nationalist-led government of Prime Minister Narendra Modi stripped Jammu-Kashmir of its statehood and divided it into two federally governed territories last year. Late Tuesday, authorities lifted a curfew in Srinagar but said restrictions on public movement, transport and commercial activities would continue because of the coronavirus pandemic. (AP Photo/Mukhtar Khan)
Workers walk in front of the main entrance of a nursing home for elderly people, where more than 60 people tested positive for Covid-19, in Burbaguena, near Teruel on August 04, 2020. (Photo by JOSE JORDAN / AFP) (Photo by JOSE JORDAN/AFP via Getty Images)
MANILA, PHILIPINES - AUGUST 4: Filipino health workers hold the syringe as they conduct the covid-19 test at the testing area in Manila, Philippines on August 04, 2020.  Philippine President Rodrigo Duterte declares that several places in the country will go back to Modified Enhance Community Quarantine (MECQ) from August 04-18, 2020 as the Coronavirus disease cases in the country exceed up to 100,000. (Photo by Dante Diosina Jr/Anadolu Agency via Getty Images)
SCHOENEFELD, GERMANY - AUGUST 04: A man wearing a protective face masks walks past a sign directing travelers to a coronavirus testing station at Schoenefeld Airport near Berlin during the coronavirus pandemic on August 4, 2020 in Schoenefeld, Germany. Authorities urge people arriving from countries deemed as higher risk, including Spain and some countries in the Balkans, though the tests are not yet a requirement. So far one percent of those tested at the Berlin airports of Tegel and Schoenefeld are showing positive for Covid-19 infection. (Photo by Sean Gallup/Getty Images)
PANCHKULA, INDIA - AUGUST 3: Police personnel screening traffic at Morni Hills, on August 3, 2020 in Panchkula, India. (Photo by Sant Arora/Hindustan Times via Getty Images)
NEW DELHI, INDIA - AUGUST 3: A family of four seen wearing face masks while travelling on a scooter at Daryaganj, on August 3, 2020 in New Delhi, India. (Photo by Sanchit Khanna/Hindustan Times via Getty Images)
French President Emmanuel Macron (R) talks with home-care assistants during a visit to Gisele Charles, 80, who lives alone in Toulon, southern France, on August 4, 2020. - Emmanuel Macron announced that the State would release 80 million euros to pay, with an equal contribution from the departments, an exceptional Covid-19 bonus for home carer. (Photo by CHRISTOPHE SIMON / POOL / AFP) (Photo by CHRISTOPHE SIMON/POOL/AFP via Getty Images)
A group of police and soldiers patrol the Docklands area of Melbourne on August 2, 2020, after the announcement of new restrictions to curb the spread of the COVID-19 coronavirus. - Australia on August 2 introduced sweeping new measures to control a growing coronavirus outbreak in its second-biggest city, including an overnight curfew and a ban on weddings for the first time during the pandemic. (Photo by William WEST / AFP) (Photo by WILLIAM WEST/AFP via Getty Images)
02 August 2020, Berlin: Three people moderate during a rally of the so-called Querfront and Corona Deniers in the amphitheater in Mauerpark. They demand the immediate cessation of all Corona restrictions. Photo: Annette Riedl/dpa (Photo by Annette Riedl/picture alliance via Getty Images)
Children wearing face masks to protect against the new coronavirus play near a street performer dressed as a statue at a shopping mall in Beijing, Sunday, Aug. 2, 2020. (AP Photo/Andy Wong)
A masked mime artist performs for tips at a busy intersection in Johannesburg, Sunday, Aug. 2, 2020 as the country marks one hundred and twenty nine days days of lockdown to prevent the spread of COVID-19. (AP Photo/Denis Farrell)
People gather for a demonstration with the slogan ‚The end of the pandemic - freedom day' - against coronavirus restrictions in Berlin, Germany, Saturday, Aug. 1, 2020. It comes amid increasing concern about an upturn in infections in Germany. (AP Photo/Markus Schreiber)
BERLIN, GERMANY - AUGUST 01: People stage a protest, which was organized by "Querdenken 711", against coronavirus (Covid-19) restrictions in Berlin, Germany on August 01, 2020. (Photo by Erbil Basay/Anadolu Agency via Getty Images)
A passenger leaves after being tested with a COVID-19 test, at the Roissy Charles de Gaulle airport, outside Paris, Saturday, Aug. 1, 2020. Travelers entering France from 16 countries where the coronavirus is circulating widely are having to undergo virus tests upon arrival at French airports and ports.(AP Photo/Thibault Camus)
Indian Muslims leave after attending an Eid al-Adha prayer service at the Jama Masjid in Ahmedabad, India, Saturday, Aug. 1, 2020. Eid al-Adha, or the Feast of the Sacrifice, is observed by sacrificing animals to commemorate the prophet Ibrahim's faith in being willing to sacrifice his son. (AP Photo/Ajit Solanki)
CARCAVELOS, PORTUGAL - JULY 30: Twins Catarina and Dalila Diniz, Cascais Community Program volunteers, wear protective masks and gloves while looking for residents in Bairro dos Diamantes to register them for serologic tests and provide masks to those in need during the COVID-19 Coronavirus pandemic, on July 30, 2020 in Carcavelos, Portugal. Some 300 volunteers participate in a program created by the Municipality of Cascais that offers a test for free for COVID-19 to every resident. Portugal registers to date 1,727 fatalities, 50,868 confirmed cases and 36,140 recovered, and the Government is to approve today changes regarding measures to combat the pandemic. (Photo by Horacio Villalobos#Corbis/Corbis via Getty Images)
A doctor (R) checks the body temperature of a man at a containment zone implemented as a preventive measure against the COVID-19 coronavirus in Chennai on July 30, 2020. (Photo by Arun SANKAR / AFP) (Photo by ARUN SANKAR/AFP via Getty Images)
Hundreds of Muslim pilgrims circle the Kaaba, the cubic building at the Grand Mosque, as they observe social distancing to protect themselves against the coronavirus, in the Muslim holy city of Mecca, Saudi Arabia, Wednesday, July 29, 2020 During the first rites of hajj, Muslims circle the Kaaba counter-clockwise seven times while reciting supplications to God, then walk between two hills where Ibrahim's wife, Hagar, is believed to have run as she searched for water for her dying son before God brought forth a well that runs to this day. (AP Photo)
Supporters of Sri Lanka Podujana Peramuna (SLPP) attend a campaign rally with Prime Minister Mahinda Rajapaksa ahead of the upcoming parliamentary elections, near the capital Colombo on July 29, 2020. - The elections were to be held on April 25, but were postponed twice due to the COVID-19 coronavirus pandemic before being rescheduled for August. (Photo by LAKRUWAN WANNIARACHCHI / AFP) (Photo by LAKRUWAN WANNIARACHCHI/AFP via Getty Images)
A man wearing a face mask walks along a street of Havana, on July 29, 2020. - Cuba has 2588 confirmed cases of COVID-19 and 87 deceased. (Photo by YAMIL LAGE / AFP) (Photo by YAMIL LAGE/AFP via Getty Images)
Silva Cossa, the caretaker, ties ribbons onto the fence to represents a South African who has died from Covid-19, at St James Presbyterian church in Bedford Gardens, Johannesburg, South Africa, Wednesday, July 29, 2020. (AP Photo/Themba Hadebe)
Passengers, wearing full protective gear to protect against the spread of coronavirus, push their luggage to check-in, as they check in to travel to Colombo, Sri Lanka, at the Zaventem international airport in Brussels, Wednesday, July 29, 2020. Europe's tourism revival is running into turbulence only weeks after countries reopened their borders, with rising infections in Spain and other nations causing increasing concern among health authorities over people bringing the coronavirus home from their summer vacations. (AP Photo/Francisco Seco)
Passengers, who were stranded following the closure of border due to the COVID-19 pandemic, wait upon their arrival from Iraqi Kurdistan to the Syrian side of the Semalka border crossing in northeastern Syria on July 29, 2020. (Photo by Delil SOULEIMAN / AFP) (Photo by DELIL SOULEIMAN/AFP via Getty Images)
A young couple embraces as the sun sets in the Balearic Islands capital of Palma de Mallorca, Spain, Tuesday, July 28, 2020. Concerns over a new wave of coronavirus infections brought on by returning vacationers are wreaking havoc across Spain's tourism industry, particularly in the Balearic Islands following Britain's effective ban on travel to the country. (AP Photo/Joan Mateu
A picture taken during a presentation to the media shows a person wearing a protective suit while collecting a cooler from a drone, which usually carries blood samples to be tested for Covid-19, on July 28, 2020 outside DOROT, Netanya Geriatric Medical Center, in the central Israeli city of Netanya. - Amid the novel coronavirus pandemic crisis, the Israeli Ministry of Transportation started a pilot project Remedy from the sky program, drones for delivery of payloads including medical items like blood samples and medicines. (Photo by GIL COHEN-MAGEN / AFP) (Photo by GIL COHEN-MAGEN/AFP via Getty Images)
Galway , Ireland - 28 July 2020; Jockeys Gary Carroll, left, and Gary Halpin walk to the parade ring prior to the COLM QUINN BMW Mile Handicap on day two of the Galway Summer Racing Festival at Ballybrit Racecourse in Galway. Horse racing remains behind closed doors to the public under guidelines of the Irish Government in an effort to contain the spread of the Coronavirus (COVID-19) pandemic. (Photo By Harry Murphy/Sportsfile via Getty Images)
A man, wearing a mask to protect against the spread of coronavirus, walks along a commercial street in Antwerp, Tuesday, July 28, 2020. Belgium’s Prime Minister Sophie Wilmes has unveiled a set of drastic social distancing measures aimed at avoiding a new general lockdown amid a surge of COVID-19 infections. After a sharp decline of infections, Belgium has witnessed a surge in the number of confirmed cases over the past three weeks, especially in Antwerp province. (AP Photo/Francisco Seco)
A health worker takes a nasal swab for COVID-19 test in New Delhi, India, Tuesday, July 28, 2020. India is the third hardest-hit country by the pandemic in the world after the United States and Brazil. (AP Photo/Manish Swarup)
NEW YORK, NEW YORK - JULY 27: A man wears a protective mask while walking 6 identical dogs as the city continues Phase 4 of re-opening following restrictions imposed to slow the spread of coronavirus on July 27, 2020 in New York City. The fourth phase allows outdoor arts and entertainment, sporting events without fans and media production. (Photo by Cindy Ord/Getty Images)
A man with suspected COVID-19 symptoms, is carried on a wheelchair together with an oxygen tank to the School Hospital in Tegucigalpa, on July 27, 2020. - At least 1,100 have died and 40,000 have been infected with COVID-19 in Honduras. (Photo by ORLANDO SIERRA / AFP) (Photo by ORLANDO SIERRA/AFP via Getty Images)
A couple waits for information on a relative hospitalized with COVID-19 symptoms, outside of the Instituto de Seguridad Social hospital in Quito, Ecuador, Monday, July 27, 2020. (AP Photo/Dolores Ochoa).
A few clients of a beachside bar and restaurant are seen drinking on the terrace. Due to the repeated outbreaks of Covid-19 in Barcelona, the bars and terraces will necessarily close at the latest at 12:00 pm. (Photo by Paco Freire / SOPA Images/Sipa USA)
Masks placed on mannequins heads are displayed outside a shop in Sarajevo's main street, Bosnia, Monday, July 27, 2020. Regional WHO office in Bosnia expressed its concern with recent reports that medical institutions around the country are closing to maximum capacity as recent spike in COVID-19 infections are reaching record levels. (AP Photo/Eldar Emric)
Passengers arriving at Birmingham Airport, as people arriving into England from holidays in Spain have been told they must quarantine when they return home.
MALAGA, SPAIN - JULY 27: British Citizens arrive at the Malaga-Costa del Sol Airport after the UK imposed a quarantine on all travellers from Spain on July 27, 2020 in Malaga, Spain. (Photo by Álex Zea/Europa Press via Getty Images) (Photo by Europa Press News/Europa Press via Getty Images)
Healthcare worker Dante Hills, left, passes paperwork to a woman in a vehicle at a COVID-19 testing site outside of Marlins Park, Monday, July 27, 2020, in Miami. The Marlins home opener against the Baltimore Orioles on Monday night has been postponed as the Marlins deal with a coronavirus outbreak that stranded them in Philadelphia. (AP Photo/Lynne Sladky)
NEW YORK - JULY 27: An outdoor dining area is seen as the city continues Phase 4 of re-opening following restrictions imposed to slow the spread of coronavirus on July 27, 2020 in New York City. Many restaurants have built outdoor seating on the streets in order to allow for social distancing between patrons. The fourth phase allows outdoor arts and entertainment, sporting events without fans and media production. (Photo by Jamie McCarthy/Getty Images)
SEOUL, SOUTH KOREA - JULY 26: A Kiwoom Heroes cheerleader dances while wearing a face mask during the KBO League game between Lotte Giants and Kiwoom Heroes at the Gocheok Sky Dome on July 26, 2020 in Seoul, South Korea. South Korean baseball start accepting fans to stadiums, ahead of other sports after new coronavirus pandemic, up to 10 percent of its capacity. (Photo by Han Myung-Gu/Getty Images)
Rev Canon Joe Morrow during the first post-lockdown baptism service in the Scottish Episcopal Church of 11 month-old Magnus Hutchwaite, at St James The Great church in Stonehaven. (Photo by Jane Barlow/PA Images via Getty Images)
An Israeli medical worker in a protective suit accompanies a man who tested positive for COVID-19, for an emergency room consultation at the Sheba Medical Center, the country's largest hospital, in Ramat Gan near the coastal city of Tel Aviv, on July 26, 2020. (Photo by JACK GUEZ / AFP) (Photo by JACK GUEZ/AFP via Getty Images)
Passengers flying from Barcelona arrive at Birmingham Airport, following an announcement on Saturday that holidaymakers who had not returned from Spain and its islands by midnight would be forced to quarantine for 14 days after Covid-19 second wave fears saw the European country struck off the UK's safe list. The decision was made after Spain recorded more than 900 fresh daily Covid-19 cases for two days running. (Photo by Jacob King/PA Images via Getty Images)
Tourist wearing protective face masks are visiting the Main Square, popular tourist destination, during coronavirus pandemic. Krakow, Poland on July 26, 2020. Very few people visiting Krakow are seen wearing protective face masks and keeping social distance while Poland's coronavirus cases has risen this weekend to 43,065 and deaths up to 1,671. (Photo by Beata Zawrzel/NurPhoto via Getty Images)
Israeli medical workers in protective gear accompany a woman who tested positive for COVID-19, for an emergency room consultation at the Sheba Medical Center, the country's largest hospital, in Ramat Gan near the coastal city of Tel Aviv, on July 26, 2020. (Photo by JACK GUEZ / AFP) (Photo by JACK GUEZ/AFP via Getty Images)
Women wearing protective face masks walk along Ocean Drive amid the coronavirus pandemic, Friday, July 24, 2020, in Miami Beach, Fla. Masks are mandated both indoors and outdoors in Miami Beach. People found not wearing a mask are subject to a civil fine of $50. (AP Photo/Lynne Sladky)
Employees dressed in maid costumes from several maid-themed cafes of Akihabara pray during a prayer-meeting for protection from COVID-19 and for a thriving business at the Kanda Myojin shrine Saturday, July 25, 2020, in Tokyo. Tokyo Gov. Yuriko Koike this week asked residents to stay home as much as possible during the long weekend, even though Prime Minister Shinzo Abe's government has gone ahead with a "Go To" tourism promotion campaign that excludes Tokyo for now to help the badly hit tourism industry. (AP Photo/Eugene Hoshiko)
Employees dressed in maid costumes from several maid-themed cafes of Akihabara pause after a prayer-meeting for protection from COVID-19 and for a thriving business at the Kanda Myojin shrine Saturday, July 25, 2020, in Tokyo. Tokyo Gov. Yuriko Koike this week asked residents to stay home as much as possible during the long weekend, even though Prime Minister Shinzo Abe's government has gone ahead with a "Go To" tourism promotion campaign that excludes Tokyo for now to help the badly hit tourism industry. (AP Photo/Eugene Hoshiko)
A child wearing a protective face mask, stands in line to receive a free meal in the Peronia neighborhood of Villa Nueva, Guatemala, Friday, July 24, 2020. The Villa Nueva City Hall delivers hot meals three times a week in a selected area of the neighborhood for residents who have been economically affected by the COVID-19 restrictions related to the government-ordered shutdowns. (AP Photo/Moises Castillo)
The lower bowl at Tropicana Field is closed off as the Tampa Bay Rays take batting practice before a baseball game against the Toronto Blue Jays Friday, July 24, 2020, in St. Petersburg, Fla. The lower bowl is closed off to keep players safe from the spread of the corona virus. (AP Photo/Chris O'Meara)
Undertakers wearing personal protective equipment (PPE) bury the casket containing the remains of Steward Motlhabane, who died of COVID-19 coronavirus, during the funeral at the Westpark cemetery in Johannesburg, on July 22, 2020. (Photo by Michele Spatari / AFP) (Photo by MICHELE SPATARI/AFP via Getty Images)
Women wearing face masks to help protect against the spread of the new coronavirus watch a mobile phone at the Gyeongbok Palace, one of South Korea's well-known landmarks, in Seoul, South Korea, Saturday, July 25, 2020. South Korea reported newly confirmed cases of COVID-19 over the past 24 hours, its first daily jump over 100 in nearly four months. (Photo/Ahn Young-joon)
A health worker prepares to take a swab sample from a man as he reacts during a medical screening for the COVID-19 coronavirus, in Ahmedabad on July 22, 2020. - India last week became the third country after the United States and Brazil to hit one million cases but many experts say that with testing rates low, the true number could be much higher. (Photo by SAM PANTHAKY / AFP) (Photo by SAM PANTHAKY/AFP via Getty Images)
An Israeli medic collects a swab sample from a girl at a COVID-19 testing facility in the Israeli city of Or Yehuda on July 22, 2020. (Photo by JACK GUEZ / AFP) (Photo by JACK GUEZ/AFP via Getty Images)
BUENOS AIRES, ARGENTINA - JULY 22: A couple wearing protective masks buy at the greengrocer's at Recoleta neighborhood on July 22, 2020 in Buenos Aires, Argentina. As number of cases hit a new daily record, Buenos Aires City continues to reopen after the official announcement to soften measures against COVID-19. Today, dog walkers, car washes, and toy industry are permitted to resume business. Other activities allowed are individual sports, worshiping in temples, and take away restaurants. (Photo by Ricardo Ceppi/Getty Images)
ARLINGTON, VA - JULY 22: A airport employee performs an aircraft disinfecting demonstration during a media preview at the Ronald Reagan National Airport on July 22, 2020 in Arlington, Virginia. During the COVID-19 pandemic all Delta employees and passengers are required to wear facemasks while onboard a Delta plane. (Photo by Michael A. McCoy/Getty Images)
Sumo spectators wearing face mask practice social distance in their seats during the outbreak of the new coronavirus as they watch the first day of the sumo tournament in Tokyo, Sunday, July 19, 2020.(Kyodo News via AP)
Indian Hindu devotees wearing masks as a precaution against the coronavirus carry offerings for Hindu goddess Kali during Bonalu festival in Hyderabad, India, Sunday, July 19, 2020. Bonalu is a month-long Hindu folk festival of the Telangana region dedicated to Kali, the Hindu goddess of destruction. (AP Photo/Mahesh Kumar A.)
In this photo released on the official Facebook page of Syrian Presidency, Syrian President Bashar Assad and his wife Asma vote at a polling station in the parliamentary elections in Damascus, Syria, Sunday, July 19, 2020. Syrians headed to polling stations in government-held parts of the war-torn country on Sunday to elect a new parliament amid strict health measures to prevent the spread of coronavirus amid an increase of cases in recent days. (Syrian Presidency via AP)
A street artist spray paints a protective face mask over an old mural featuring a Venezuelan Indigenous man, in Caracas, Venezuela, Saturday, July 18, 2020, amid the new coronavirus pandemic. (AP Photo/Matias Delacroix)

At the weekend, the New York Times reported that hundreds of scientists say there is evidence that novel coronavirus in smaller particles in the air can infect people.

Until now, the WHO has said the coronavirus disease spreads primarily from person to person through small droplets from the nose or mouth, which are expelled when a person with Covid-19 coughs, sneezes or speaks.

In an open letter to the agency, which the researchers plan to publish in a scientific journal next week, 239 scientists in 32 countries outlined the evidence showing smaller particles can infect people, the NYT said.

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