Covid-19 rarely spreads through surfaces. So why are we still deep cleaning?

‘Armed with a year’s worth of data about coronavirus cases, researchers say one fact is clear. It’s people, not surfaces, that should be the main cause for concern. Evidence from superspreading events, where numerous people are infected at once, usually in a crowded indoor space, clearly point to airborne transmission, says Marr. “You have to make up some really convoluted scenarios in order to explain superspreading events with contaminated surfaces,” she says.

‘Hand washing is crucial, says Marr, because surface transmission can’t be ruled out. But it’s more important to improve ventilation systems or to install air purifiers than to sterilize surfaces, she says. “If we’ve already paid attention to the air and we have some extra time and resources, then yes, wiping down those high-touch surfaces could be helpful,” she says.

‘Households can also ease up, says Pickering. Quarantining groceries or disinfecting every surface is going too far. “That’s a lot of work and it also is probably not reducing your exposure that much,” she says. Instead, reasonable hand hygiene, as well as wearing a mask and social distancing to reduce exposure from close contacts is a better place to focus efforts.’

Read here (Nature, Jan 29, 2021)

As system buckles, MOH cuts down testing of close contacts

‘With the healthcare system at breaking point due to the surge in the number of Covid-19 patients, the Ministry of Health is trying several new approaches to ease the burden. Yesterday, the ministry issued a new circular containing changes in contact tracing and priority for swab tests.

‘According to Health Ministry sources, they would no longer test every individual identified as close contacts to Covid-19 positive patients and instead only test those with symptoms. "All close contacts must be identified, ordered to undergo isolation and monitoring at home. However, Covid-19 screening test would be done only on close contacts who are symptomatic," said the notice sighted by Malaysiakini.’

Read here (Malaysiakini, Jan 14, 2020)

Infected after 5 minutes, from 20 feet away: South Korea study shows COVID-19's spread indoors

‘KJ Seung, an infectious disease expert and chief of strategy and policy for the nonprofit Partners in Health’s Massachusetts COVID response, said the study was a reminder of the risk of indoor transmission as many nations hunker down for the winter. The official definition of a “close contact” — 15 minutes, within 6 feet — isn’t foolproof.

‘Lee and his team recreated the conditions in the restaurant... “Incredibly, despite sitting a far distance away, the airflow came down the wall and created a valley of wind. People who were along that line were infected,” Lee said. “We concluded this was a droplet transmission, and beyond two meters.”

“Eating indoors at a restaurant is one of the riskiest things you can do in a pandemic,” she [Linsey Marr, a civil and environmental engineering professor at Virginia Tech who studies the transmission of viruses in the air] said. “Even if there is distancing, as this shows and other studies show, the distancing is not enough.”

Read here (LA Times, Dec 12, 2020)

Stop wiping down groceries and focus on bigger risks, say experts on coronavirus transmission

“To the best of my knowledge, in real life, scientists like me — an epidemiologist and a physician — and virologists basically don’t worry too much about these things,” said David Morens, a senior adviser to the director of the National Institute of Allergy and Infectious Diseases, Anthony S. Fauci... 

‘But public confusion about the coronavirus and surfaces is understandable, said Angela Rasmussen, a virologist at the Center for Infection and Immunity at Columbia University’s Mailman School of Public Health. “Scientists really haven't really done a very good job of explaining how you get evidence for different types of transmission or different transmission routes.” Finally, she said, it’s important to remember that “viruses have to have a host and they can’t replicate without one. So … the main place that’s going to be the source of virus in anybody’s household is going to be the people in it and not the surfaces or the physical environment.” “Even if there’s virus kicking around on certain things,” she said, “that risk can really be mitigated practically by washing your hands.”

Read here (Washington Post via MSN, Oct 23, 2020)

Knowing Covid-19 was at their door, family of 8 planned strategy to fight it

‘When Aman Gwjwn, 17, developed a persistent cough and cold in July while on holiday at her grandmother's home in Bangalore, her family of eight went to war, preparing themselves for Covid-19 to sweep through their home. Everyone from a 14-year-old eighth-grade student to a near-octogenarian would go on to be infected. But the Chinese-Indian family slowly won their battle against the disease over the next 1½ months, armed with discipline, composure and logistical planning.

"Our approach was: We'll all surely get it, but we'll all survive it as a family. We just made sure everyone didn't fall sick together, so that some people were healthy enough to take care of the others," said Ms Jennifer Liang, 48, Aman's mother and a social worker in Assam who flew to Bangalore immediately. The Liangs formed what they called "a war council" of decision makers, which included Jennifer's husband Sunil Kaul, a doctor and public health activist in Assam. As Aman isolated herself in her uncle's house nearby, the family set up a WhatsApp group called Covid Planning.’

Read here (Straits Times, Sept 26, 2020) 

Household contacts over 6 times more likely to become infected: South Korea study

‘A recent study by researchers in South Korea, published in the US CDC’s Emerging Infectious Diseases journal, found that SARS-CoV-2 transmission was far more common in household settings compared to public settings. Based on analysis of more than 59,000 contacts of more than 5,700 COVID-19 “index patients,” the researchers found that household contacts were more than 6 times more likely to become infected than non-household contacts. The study identified cases in 11.8% of household contacts, compared to only 1.9% of non-household contacts.

‘Notably, households with an “index patient” aged 10-19 years were at even higher risk for transmission—cases identified in 18.6% of household contacts, compared to 11.8% in households with “index patients” of other ages. The lowest transmission risk among household contacts was for “index patients” aged 0-9 years. In these households, cases were identified in only 5.3% of household contacts; however, this was still greater than the overall risk for non-household contacts. This indicates that children who are infected at school could transmit the infection at home more easily than in other settings, particularly for older children, which would put other family members at increased risk.‘

Source: Newsletter, Center for Health Security, John Hopkins University.

Read here (EID Journal, 2020)

How to avoid the virus as the world reopens

‘Three key factors determine risk of exposure: proximity to people; duration of exposure; and how confined the environment is. The greatest peril lies where the three overlap. “The biggest risk is being in close proximity to someone in an indoor space for any extended period of time,” said Jeremy Rossman, honorary senior lecturer in virology at the University of Kent. The perception of risk and the actual scientific risk have sometimes diverged, he noted. “I don’t think that’s been very clearly communicated”.’

Read here (Financial Times, June 10, 2020)

Wearing face masks at home cuts Covid-19 spread by 79 percent - study

‘While face masks and frequent disinfection is widely assumed to prevent Covid-19 transmission, a new study has lent weight to the usefulness of these measures in ‘real world’ situations. In a paper published in the journal BMJ Global Health yesterday, researchers found that wearing face masks at home before the primary case showed symptoms slashed the risk of secondary infections by 79 percent. Wearing masks after symptoms appeared had no effect.’

Read here (Malaysiakini, May 29, 2020)

Experiment shows human speech generates droplets that linger in the air for more than 8 minutes

‘Ordinary speech can emit small respiratory droplets that linger in the air for at least eight minutes and potentially much longer, according to a study published Wednesday that could help explain why infections of the coronavirus so often cluster in nursing homes, households, conferences, cruise ships and other confined spaces with limited air circulation.

‘The report, from researchers at the National Institute of Diabetes and Digestive and Kidney Diseases and the University of Pennsylvania, was published in the Proceedings of the National Academy of Sciences, a peer-reviewed journal. It is based on an experiment that used laser light to study the number of small respiratory droplets emitted through human speech.’

Read here (The Washington Post, May 14, 2020)

Higher transmission rate among household contacts and individuals traveling with infected people

‘The researchers found that household contacts of COVID-19 cases and individuals traveling with cases were both at elevated risk of infection. Additionally, the secondary “attack rate” (percentage of contacts who tested positive for SARS-CoV-2 infection) among household contacts was at least 11.2%. While attack rates were higher among older adults, the value for children—7.4% and 7.1% for children aged 0-9 years and 10-19 years, respectively—was higher than in younger and middle-aged adults—4.9%-6.1% for adults aged 20-29 years, 30-39 years, and 40-49 years. Individuals aged 0-39 years exhibited lower risk of severe COVID-19 than adults aged 40 years and older.’

Read here (The Lancet, April 27, 2020)

From ‘gold standard’ to a coronavirus ‘explosion’: Singapore battles new outbreak

‘There were warning signs before the new outbreak. On Feb. 10, after a Bangladeshi labourer became the first to be infected with the virus, lawyer Dipa Swaminathan, founder of It’s Raining Raincoats, an initiative that works with migrants, wrote a Facebook post warning that ‘the spread among them could be rapid, given the cramped conditions in which they live, work and are transported.’

‘Health officials said the man had visited Mustafa Center, a giant shopping complex in Singapore’s Little India district that is popular with foreign workers.

‘But as recently as two weeks ago, shoppers were going in and out of the building without temperature checks, and few employees were seen wearing masks. On Tuesday, the government said 86 infections had been linked to Mustafa Center.’

Read here (Los Angeles Times, April 14, 2020)

The second wave: How did the fight go wrong? (Singapore)

‘The government was blindsided by the spread among our foreign workers... But it needs to be pointed out that the new cases outside this group is worrying in itself. Of the record 287 new cases reported two days ago on 9 April (surpassed again yesterday), 202 were linked to foreign worker dormitories. But a large number (85 cases) were not, including 48 unlinked to existing cases. We are now fighting the virus now on not one but two raging fronts.’

COMMENT: The second front could have been opened up due to an underestimation of how effectively the virus could spread within the community especially by asymptomatic carriers

Read here (Tan Tarn How, April 11, 2020)

WHO issues guidelines on the use of masks in community, homecare and healthcare settings

‘This document provides advice on the use of masks in communities, during home care, and in health care settings in areas that have reported cases of COVID-19. It is intended for individuals in the community, public health and infection prevention and control (IPC) professionals, health care managers, health care workers (HCWs), and community health workers. This updated version includes a section on Advice to decision makers on the use of masks for healthy people in community settings.’

Read here (WHO, April 6, 2020)

Modes of contact and risk of transmission in COVID-19 among close contacts

A new preprint on medRxiv examines the modes of contact and the level of transmission among close contacts of persons infected with COVID-19. The study follows just under 5,000 close contacts in Guangzhou, China. Of the close contacts identified, 2.6% of cases developed symptoms during their quarantine, the majority of which were mild or moderate cases (89.9%) and a small portion of which were asymptomatic (6.2%). They authors found that contacts within the same household were at the highest risk of contracting COVID-19.

Read here (Medrxiv, March 26, 2020)

Note: As the Covid-19 situation worsens in the US, Europe and other countries, our students and other citizens are coming home in large numbers. They are being told to self-quarantine. Many are doing it at home, in which case they may infect others if they are carrying the virus. Some are sending their folks to AirBNBs.