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I’ve always wondered: why many people in Asian countries wear masks, and whether they work


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Face masks are a common sight in Asia. Why?
David Chang/AAP

C Raina MacIntyre, UNSW and Abrar Ahmad Chughtai, UNSW

This is an article from I’ve Always Wondered, a series where readers send in questions they’d like an expert to answer. Send your question to alwayswondered@theconversation.edu.au


In Japan, many people wear face masks – is that to prevent the wearer getting the infection, or is the wearer already infected and protecting those around? Is the mask useful in protecting against viruses or bacteria? – Petrina, Greenwich

Thanks for your question, Petrina. You’re right, in countries like Japan and China, facemask use in the community is widespread – much more so than in Western cultures. People wear them to protect the respiratory tract from pollution and infection, and to prevent the spread of any pathogens they might be carrying.

Whether this works depends on the type of mask.

There are three supposed ways a mask can provide protection: by providing a physical barrier (which prevents splashes and sprays), by filtering the particles (blocking particles of a certain size from entering the respiratory tract), and by fitting around the face to prevent leakage of air around the sides.

Some mask makers have also gone the extra step of using antimicrobials and claim to kill bugs on the surface of the mask, but these haven’t been tested to see if they provide any benefit.

Healthcare workers have been using cloth masks (made of cotton or other materials and with ties to secure them at the back) while caring for patients since the late 19th century to protect from various respiratory infections such as diphtheria, scarlet fever, measles, pandemic influenza, pneumonic plague and tuberculosis.

Cloth masks have been around since the late 19th century.
Author provided



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During the mid 20th century, disposable surgical facemasks (similar in look to the cloth masks but made of paper) were developed. Surgical masks were developed to prevent the surgeon from contaminating the wound during surgery, but studies have not proven they help.

Surgical masks have no evidence of effectiveness.
from http://www.shutterstock.com

These were followed by respirators, which vary in shape and material but are designed to fit around the face and filter particles. Respirators are designed specifically to protect the respiratory tract from inhaled germs. There are many types, which may be reusable or disposable.

People must undergo fit-testing to ensure respirators are correctly fitted, with a good seal around the face. Unlike masks, respirators are subject to certification and regulation, and are proven to protect against respiratory infection.

Respirators are proven to protect against infection.
from http://www.shutterstock.com

Surgical masks are unregulated for filtration and do not fit around the face, and the evidence for their use is less convincing. In a community study, families with a sick child who wore such a mask were less likely to get sick if they also wore a mask, but many family members didn’t wear their masks all the time.

In a university setting, students were protected from sick classmates if they wore the mask within 36 hours of their classmate getting sick.

In many low income countries, the cost of even paper surgical masks is prohibitive, so cloth masks are used, washed and re-used. But these don’t protect against infection, and may even increase the risk of infection.

Prevention of infection vs source control

Masks can be used to protect healthy people (such as nurses and doctors) from exposure to infection, but are also used by sick people (such as a TB patient) to prevent spread of infections to others (called “source control”). There is less research on this use than on the use of masks by well people. The efficacy of source control is unknown.




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Do masks work?

It’s long been thought surgical masks protect from transmission of pathogens, which spread through the air on large, short-range droplets, while respirators protect against much smaller, airborne particles, which may remain suspended in the air for several hours and transmit infection over long distances. So most guidelines recommend a mask for droplet transmitting infections (such as influenza) and a respirator for airborne infections (such as TB and measles).

But we’ve shown respirators protect better than masks even against droplet-spread infections. And the longstanding belief that infections neatly fit into either droplet or airborne transmission is not correct. Respiratory transmission of infections is more complex than this.

To say whether masks work, we have to specify whether we’re talking about a respirator, a surgical mask or a cloth mask.

The respirators are the Rolls Royce option and do protect, and this is a tool for frontline health workers facing epidemics of known and unknown infections. Surgical masks probably also protect but to a lesser extent. But there’s no evidence cloth masks will protect against invading or escaping bugs.


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C Raina MacIntyre, Professor of Infectious Diseases Epidemiology, Head of the School of Public Health and Community Medicine, UNSW and Abrar Ahmad Chughtai, Epidemiologist, UNSW

This article was originally published on The Conversation. Read the original article.

Five active volcanoes on my Asia Pacific ‘Ring of Fire’ watch-list right now


Heather Handley, Macquarie University

In Indonesia, more than 197 million people live within 100km of a volcano, including more than 8.6 million inside a 10km radius.

The country has a record of some of the most deadly volcanic eruptions in history, and right now there are ongoing eruptions at the Agung, Sinabung and Dukono volcanoes. But other volcanoes in the region are active too, including Kadovar in Papua New Guinea, Mayon in the Philippines, and Kusatsu-Shiranesan in Japan.

Although it all seems to be happening at once, it’s normal for the Asia-Pacific region to have frequent earthquake and volcanic activity.

But we still need to keep a close eye on things, and local volcanic authorities are monitoring activity to manage risks and evacuations adequately.




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The Ring of Fire extends around the Pacific Rim in a horseshoe shape.
Earth Observatory of Singapore

These volcanoes are part of the Pacific “Ring of Fire”, a horseshoe-shaped belt of earthquakes and volcanoes that runs for some 40,000km, roughly around the edge of the Pacific Ocean. The Ring stretches from South America, up to North America and across the Bering straight, and down through Japan, the Philippines, Papua New Guinea, Vanuatu and New Zealand. It generates around 90% of the world’s earthquakes and contains 75% of its active volcanoes.

Here are the volcanoes on my Asia-Pacific watch list this week.

Agung, Bali, Indonesia

Mount Agung in Bali has been highly scrutinised for the past few months, largely because of Bali’s popularity as a tourist destination.

After a series of volcanic earthquakes (more than 1,000 per day at its peak), eruptions began on November 21, 2017.




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Since then we’ve seen frequent explosive eruptions emitting gas, steam and volcanic ash reaching thousands of metres above the volcano.

Drones used by the Indonesian Centre for Volcanology and Geological Hazard Mitigation (CVGHM) show an estimated 20 million cubic metres of new lava in the crater, filling roughly one-third of it.

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In the evening of January 19 an explosion of fire (known as a “strombolian” eruption) ejected glowing rocks up to 1km from the crater. The alert level remains at the highest level, with an exclusion zone in place.

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There have been very few issues for tourists visiting Bali so far, apart from a temporary closure of Denpasar airport in late November 2017. However, thousands of Agung’s local residents are still displaced from their homes, with many still stationed in evacuation centres. It remains uncertain when those living closest will be able to return home.

Many evacuated pregnant women have given birth to babies since leaving their homes in places such as the Bumi Sehat’s community health center and birthing clinic in Ubud, which relies on donations to keep running. As a mother of a one-year-old and a three-year-old, I can’t imagine having a newborn baby and not being in the comfort of my own home.




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Sinabung, Sumatra, Indonesia

Sinabung volcano awoke in 2010 after a 400-year sleep, and is currently one of the most active volcanoes in Indonesia. It has been pretty much in constant eruption since September 2013, and there are still frequent volcanic earthquakes.

Eruptions have produced ash plumes reaching as high as 11km into the atmosphere, as well as ash fall and lava flows. There have also been volcanic mudflows (“lahars”) and fast-moving, hot flows of gas, ash and rock fragments (“pyroclastic flows”), which have killed 25 people.

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The initial activity in 2010 saw around 30,000 people evacuated. In August last year the Indonesian National Disaster Management Authority (BNPB) reported that there were 7,214 people displaced, and a further 2,863 living in refugee camps. For the locals, life seemingly goes on in the midst of eruptions.

The alert level currently remains at 4 (on a scale of 1-4), with exclusion zones of 3-7km around the volcano.




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Mayon, Luzon, Philippines

Mayon, around 330km southeast of Manila, is a picture-perfect volcano with its steep-sided conical cone, typical of stratovolcanoes. It is one of the most active volcanoes in the Philippines, with 24 confirmed eruptive periods in the past 100 years. Mayon’s most violent eruption in 1814 killed more than 1,200 people and destroyed several towns.

The recent eruption began on January 13, 2018, and is continuing, with several episodes of dramatic lava fountaining, one lasting 74 minutes.

Eruptions during January 23-29 generated 3-5km-high ash plumes and multiple pyroclastic flows, which travelled more than 5km down drainage channels. The alert is at level 4 (on a scale of 1 to 5) and an 8km danger zone is in place.

Lava flows have currently made their way up to 4.5km down river valleys from the summit crater.

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) estimated on January 27 that the total volume of material deposited from ash fall and pyroclastic flows amounted to 10.5 million cubic metres. Remobilisation of this loose volcanic material by rainfall to form volcanic mudflows is a major concern.

According to news articles, more than 75,000 people have been evacuated, along with the temporary closure of Legazpi airport around 15km away.

Kadovar, Papua New Guinea

Until January 2018, when it began erupting, I hadn’t heard of Kadovar. It’s a 2km-wide, 365m-high emergent summit of a stratovolcano off the coast of Papua New Guinea.

Kadovar island off the coast of PNG is currently an active volcano.
Samaritan Aviation

The volcano had no confirmed historic eruptions before 2018. However, it is possible that William Dampier, a 17th-century pirate and later maritime adventurer, witnessed an eruption at Kadovar during a voyage in search of Terra Australis.

Activity began on January 5, 2018, with rising plumes of ash and steam from the volcano. The island’s inhabitants, some literally living on the crater rim, began evacuating at that time. People were initially taken by boat to neighbouring Blup Blup island but then to the mainland along with other nearby islanders, due to the close proximity of the eruption and logistics of providing people with supplies.

The Rabaul Volcano Observatory reported that activity significantly escalated on January 12, with a large explosive eruption and volcanic rocks ejected to the south. Large amounts of sulfur dioxide have been detected since January 8, and continue to be released along with ash and steam plumes. A lava “dome” has been observed glowing at night.

The impact from the eruption is not just confined to those on Kadovar and nearby islands, with satellite imagery tracking an ash plume from Kadovar travelling over tens of kilometres.

Identified volcanic risks at Kadovar include further potential explosive activity, landslides, and resulting possible tsunamis.

Kusatsu-Shirane, Honshu Japan

On January 23, 2018, an eruption occurred at Kusatsu-Shirane volcano without any prior warning, catching Japan’s Meteorological Agency and volcanic experts, not to mention the skiers on the volcano, by surprise.

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According to agency’s volcanology division, there had been no volcanic activity at the apparent site of the eruption (Kagamiike crater), for about 3,000 years.

The eruption ejected a black plume of ash and larger volcanic material that damaged a gondola and the roof of a mountain lodge.

The ejected volcanic rocks, which landed up to 1km away from the vent, injured several people. A member of the Ground Self-Defence Force who was skiing in a training exercise was killed.

The Japan Meteorological Agency has since analysed the deposits of the eruption and state that there was no new magma erupted on January 23.

Volcanic rocks were ejected from the Kusatsu-Shirane volcano.

Japan has more than 100 active volcanoes, with many monitored 24/7 by Japan’s Meteorological Agency.

Living near volcanoes

Indonesia, the Philippines and Japan have the greatest numbers of people living within 100km of their volcanoes. The populations of small volcanic island nations, such as Tonga and Samoa, almost all live within 100km.

The top 10 countries for population within 100 km of a volcano (left) and the top ten countries (area over 31,415 km²) for percentage of the total population (right).
Sarah Brown and co-authors.

Indonesia has the greatest total population located within 10km (more than 8.6 million), 30km (more than 68 million) and 100km (more than 179 million), and a record of some of the most deadly volcanic eruptions in history.

The eruption of Tambora in 1812-15, was the largest eruption in the last 10,000 years and killed around 100,000 Indonesians (due to the eruption and the ensuing famine). The infamous eruption of Krakatau (Krakatoa) killed an estimated 35,000 people, almost all due to volcanic-generated tsunamis. Volcanic mudflows (lahars) generated by the eruptions of 1586 and 1919 at Kelut (Kelud) in Java took the lives of 10,000 and 5,000 people, respectively.

The ConversationKeeping watch on the world’s volcanoes is a big job for the local volcanic agencies. This is particularly true when volcanoes erupt for the first time in history (Kadovar is a good example) or there were no warning signals before eruption, as at Kusatsu-Shirane.

Heather Handley, Associate Professor in Volcanology and Geochemistry, Macquarie University

This article was originally published on The Conversation. Read the original article.