Wiping clean the ‘mixing pot of viruses’: Lessons from a flu outbreak in a primary school

SINGAPORE – Contaminated surfaces such as a water cooler and toilet door could have played a role in a flu outbreak at a primary school in north-western Singapore last year, experts from the Ministry of Health (MOH) reported in findings published last month.

While not possible to pinpoint if that was the main mode of transmission, the experts called for hygiene and cleaning standards to be stepped up to control outbreaks.

“Given the high potential for spread of viruses in schools, adequate cleaning of the environment would be critical for an outbreak control,” a team of seven members from MOH’s Public Health Group wrote in the quarterly Epidemiological News Bulletin. “Strategies need to be put in place for schools and other organisations to manage and contain outbreaks early.”

The outbreak last April in the primary school, which was not named, affected 72 students (mostly in Primary 6) and nine staff. MOH was informed and sent a team to investigate. The team took swabs from staff and students, as well as from various surfaces close to the classroom with the most number of flu cases.

In addition to measures that the school took to curb the outbreak – which included segregating recess break times to prevent Primary 6 students from mixing with others – the MOH advised the school to focus on high-touch areas during routine cleaning.

The ministry also recommended the school use separate mops or mop pails to clean vomit, and to properly disinfect the mops after use.

While the spread of flu via droplets when an infected person sneezes, coughs or even talks is well-known and was almost certainly present in this case, the MOH’s findings have cast the spotlight on a less common transmission route.

Studies have found that influenza viruses remain viable on hard, non-porous surfaces such as metal, wood and plastic for 24 to 48 hours, which can theoretically cause infections if picked up from such surfaces and transferred to the mouth or nose, said Associate Professor Hsu Li Yang, head of the infectious diseases programme at the Saw Swee Hock School of Public Health in the National University of Singapore.

It is important for schools and childcare centres to have a proper cleaning programme, he said.

Infectious disease expert Leong Hoe Nam from Mount Elizabeth Novena Specialist Centre said: “The recent MOH report suggests that schoolchildren are constantly exposed to viruses. High-touch surfaces are like a mixing pot of viruses found in the classroom.” 

Young children with influenza play an important role in the spread of the virus to the public and other high-risk groups in the population, he said.

Citing a 2001 study in the New England Journal of Medicine, Dr Leong said: “When flu jabs were made compulsory for school children in Japan, all causes of death and influenza-related deaths in the elderly fell drastically. But when the law was repealed, the number of deaths went up subsequently.”

Influenza A outbreaks are not uncommon in Singapore and studies have shown that they are easily propagated in schools.

Seasonal flu circulates in Singapore all year round, but an increase in cases is typically seen from April to July and from November to January, which coincides with the winter flu seasons in the southern and northern hemisphere, respectively, MOH said.

Young children are one of the at-risk groups for flu-related complications and deaths.

The good news is, influenza viruses are fragile and easily killed “in a matter of seconds” when exposed to ordinary detergent or water, Dr Leong said.

In contrast, non-enveloped viruses such as the enterovirus, which can cause hand foot mouth disease, are hardier and can survive even when exposed to detergent, he said.

Contact with supermarket trolley handlebars and child rides was identified as the main cause of the outbreak of hand, foot and mouth disease in Penang last month.

'SCHOOLS REGULARLY CLEAN SURFACES'

There are established processes and procedures for schools and institutions to notify MOH of infectious diseases, the ministry told TODAY.

“If there is a cluster of cases, the school premises will be disinfected and students’ well-being will be closely monitored. Schools also take guidance from the relevant health authorities to intensify efforts where necessary.” 

Students and staff members are reminded to practise good hygiene, monitor their health and seek medical attention if they are unwell.

Schools conduct regular cleaning of equipment and surfaces that children come into contact with, MOH added. They also make hand sanitisers and masks available for use where required and conduct temperature-taking for students.

The same applies at MOE Kindergartens, where prevention measures include daily visual screening and temperature checks on all children.

E-Bridge Pre-School at Edgedale Plains, a large childcare centre that can accommodate up to 500 children, said that its measures to minimise the spread of infections include the use of a mass temperature infra-red measurement system.  It also places individually assigned shoe cabinets outside the classrooms and staff conduct physical checks before children can enter the classroom.

The building is also designed in a manner that reduces the chances of infection spread. Ms Josephine Wong, E-Bridge Pre-School’s planning and development director, said that each of the five semi-circular pods in the school can be isolated, for instance. 

Parents and caregivers also play a critical role and should check their children for signs of infection in the morning and keep unwell children at home, she said.

PERSON-TO-PERSON DROPLET SPREAD MORE LIKELY

Contaminated surfaces aside, the experts told TODAY that influenza is most likely transmitted person-to-person via droplets.

Droplets expelled by an infected person can travel up to 2m when he coughs or sneezes, Assoc Prof Hsu said.

A colder environment helps sustain the viability of the virus, which means that air-conditioning is bad news, Dr Leong said.

“If you sneeze inside a room with a temperature of around 30°C, the virus can still be found in the air for up to an hour. At around 21°C to 24°C, it will easily stay in the air for three hours. If there is a child with influenza in the classroom, and lessons are conducted in an air-conditioned room, you won’t only be sharing laughter and tears but also viruses,” Dr Leong added.

Annual vaccination is one of the best methods to protect against influenza, the doctors said.

“I call it the ‘buy one, get one free’ shot,” Dr Leong said. “Not only does the child have better school attendance and not have to worry about falling sick during exams, it also indirectly protects the elderly at home.”

Yearly flu vaccinations are recommended as flu viruses change over time, rendering older vaccines ineffective, Assoc Prof Hsu said.

Depending on the match, the efficacy of a flu vaccine can range from around 50 to 60 per cent to over 90 per cent, Dr Leong said.

Even if the person who has gotten the flu shot gets influenza, it would mitigate the severe effects of influenza.

“Although the influenza vaccination does not work exceptionally well for an individual, better herd immunity develops when more people get vaccinated,” Assoc Prof Hsu said.

STOPPING THE SPREAD: TIPS FOR PARENTS AND CAREGIVERS

Ms Josephine Wong, planning and development director at E-Bridge Pre-School, shared some tips on protecting school-going children from infections:

• Keep sick children at home. A child should be fever-free (without the assistance of medication) for 24 hours before returning to school
• Note that a child's temperature is lowest in the morning, so a low temperature on awakening is often not a true indicator of wellness. If a child has been given paracetamol or its equivalent the previous night, this medication could still be at work in lowering the child's temperature
• Parents contacted during the school day to pick up their sick child must make arrangements to fetch their child from school with urgency. Ensure that emergency contact numbers are regularly updated
• Get the child back to school at the expiry of the medical certificate given by the doctor and when all symptoms of the illness have passed. Returning to school too early may mean that the child has reduced immunity to other viruses or bacteria that may be present in school
• It is recommended that the child has no social contact outside of school during his or her contagious period