Weekly flu activity highest since 2024; doctors say haze can worsen respiratory conditions

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SINGAPORE: Influenza activity has climbed to its highest level in 32 months, with doctors reporting a surge in patients seeking treatment for respiratory issues as Singapore continues to grapple with hazy weather. 

Latest weekly statistics from the Communicable Diseases Agency (CDA) show that 44 per cent of respiratory samples tested positive for influenza from Sep 27 to Oct 3. 

The figure is more than double the 20 per cent recorded at the start of August, before the haze first crossed into the unhealthy range in early September, and the highest since weekly data began in February 2024. 

Health Minister Ong Ye Kung told reporters on Sunday (Oct 11) that emergency departments had seen a week-on-week increase in patients with respiratory issues, with polyclinics also reporting more such cases. 

The Ministry of Health (MOH) said in a statement to CNA last Thursday that polyclinics and public hospitals have haze response measures in place, which are activated according to prevailing air quality conditions.

There are sufficient medical supplies to treat haze-related conditions, MOH said, adding that healthcare institutions routinely monitor their stocks to ensure they can meet increased demand during prolonged haze episodes.

At Singapore General Hospital (SGH), Dr Chew Si Yuan, a consultant at the department of respiratory and critical care medicine, said influenza is currently the predominant cause of respiratory infection seen among patients.

“We experience flu cases all year round in Singapore … but certainly in the last one month, we have been seeing more cases than normal. Anecdotally, we have easily seen double or triple the number of cases that we normally would see,” he said.  

Dr Chew added that measures have been put in place to cope with the increase in cases. 

“All hospitals, including SGH, have surge preparedness plans in place. We are currently managing these cases with dynamic surge staff deployment,” he said. 

During periods of haze, SGH uses air purifiers and closes the windows and doors of non-air-conditioned wards. It also steps up monitoring of higher-risk patients and offers home medication delivery to reduce unnecessary trips to the hospital. 

Doctors say poorer air quality can aggravate respiratory conditions, particularly among older people, young children, pregnant women and those with underlying lung or heart conditions. 

HAZE CAN AGGRAVATE RESPIRATORY CONDITIONS 

However, there is currently no strong evidence that haze makes influenza itself more severe, according to the CDA. 

“If you have more cases, then of course there may be more severe cases overall. But currently, there's no increase in severity compared to (previous periods),” said Professor Lim Poh Lian, group director of CDA’s Communicable Diseases Programmes. 

She added that the link between haze and influenza severity has not been well-studied, and there is insufficient evidence to conclude that haze leads to worse outcomes once a person contracts influenza. 

“In general, air pollution can irritate the respiratory system, and those with chronic heart and lung disease may have more trouble once there is air pollution,” Prof Lim said. 

“But in general, there's very little evidence at this time that it causes worse influenza.” 

Dr Esther Pang, a senior consultant at Tan Tock Seng Hospital’s department of respiratory and critical care medicine, described the haze as a “contributing or triggering factor rather than the main cause” of respiratory deterioration. 

“Patients with concomitant influenza or other respiratory infection can get more inflammation as a result of both the infection as well as the effects of the haze … but they may not necessarily be more serious than usual,” she said. 

MOH says it closely monitoring the situation, and is not aware of any deaths or cases requiring intensive care due to the haze. 

PM2.5 LINKED TO RISE IN EMERGENCY VISITS 

Still, one concern is PM2.5, or fine particulate matter measuring 2.5 micrometres or less, which is commonly found in haze. Haze is not a single pollutant, but a mixture of particles and gases.

“The PM2.5 particles are very small, small enough to get past our natural filtration systems in our nose and upper airways. When they go deep into the lungs, they cause inflammation, which can affect the whole body,” said Dr Chew. 

Research by Duke-NUS Medical School and SGH using national data over a six-year period between 2016 to 2022 found an association between PM2.5 levels and emergency department visits for asthma and chronic lung disease. 

For every 10-point increase in PM2.5, emergency department visits for respiratory conditions rose by about 3 per cent, the study found. 

However, the impact may only become apparent over the following days, said Professor Marcus Ong, director of Duke-NUS’ health services and systems research programme. 

“When there's a spike in air pollution, you may not see an immediate effect,” he said. “But what you do see is that within the next two days, there's an increase in the number of these cases presenting to the emergency department.” 

Health Minister Ong has urged people with less serious respiratory symptoms to instead seek treatment at public health preparedness clinics, rather than emergency departments, which should be reserved for serious conditions.

VACCINATION, REDUCING EXPOSURE AMONG PRECAUTIONS 

MOH said short-term exposure to haze – defined as continuous exposure to unhealthy daily average PSI levels over a few days – may cause irritation of the eyes, nose and throat.

Poor air quality may also worsen symptoms in people with existing respiratory conditions such as asthma and chronic obstructive pulmonary disease.

Doctors and health authorities advised people, particularly those in vulnerable groups, to keep their influenza vaccinations up to date and limit their exposure to poor air quality. 

Asthma patients are also advised to use their prescribed preventer medication rather than relying only on reliever inhalers when they become breathless. 

People who contract influenza should stay home when unwell, wear a mask and minimise social interactions. They should seek medical attention if their condition worsens or symptoms persist. 

People should also reduce prolonged or strenuous outdoor activity when air quality warnings are in place.