According to the Centre for Health Protection (CHP) of the Department of Health, flu season in Hong Kong usually lasts from January to March and from July to August. 

Although duration of flu season varies each year, Dr Ka-Hing Wong, controller of the CHP, spoke to SCMP in January that a flu season generally lasts for around 16 weeks.

Winter flu season

This year, CHP has announced on January 10 that Hong Kong has entered the 2017-18 winter influenza season, as local seasonal influenza activity has continued to increase in the past week and exceeded the baseline level. 

As of February 7, according to CHP's Flu Express, local influenza activity remained at a high level. Since the start of the 2017/18 winter influenza season, 214 adult cases of Intensive Care Unit or death with laboratory confirmation of influenza were recorded, in which 121 of them were fatal. Also, 13 paediatric cases of influenza-associated complication/death were recorded, causing two death.

The Hospital Authority (HA) Chairman, Professor John Leong (centre), visited the wards at Tseung Kwan O Hospital on 27 December, 2017. Photo credit: GovHK
The Hospital Authority (HA) Chairman, Professor John Leong (centre), visited the wards at Tseung Kwan O Hospital on 27 December, 2017. Photo credit: GovHK

According to CHP's Flu Express last year which indicated the end of the winter influenza season, 71 severe cases, including 42 deaths, were recorded cumulatively since the activation of the enhanced surveillance from April 12 to February 24, 2017.

For the winter season in early 2016, 409 adult severe cases, including 211 deaths, and 27 paediatric cases, including three deaths, were filed. 

In Mainland China, the overall influenza activity in both southern and northern parts has also been on the rise. The positive percentage of influenza detections has increased to 42.8% in the week ending January 10, with the predominating virus being influenza B. In Guangdong, in the week ending December 31, the proportion of influenza-like illness (ILI) cases among sentinel hospitals was 6.32% while the percentage of respiratory specimens tested positive for influenza was 31.98%.

Meanwhile, for Macao, surveillance data showed that the number of reported influenza cases in the first week of 2018 was 152, higher than 89 in the previous week.

Summer flu season

In 2017, Hong Kong experienced one of its worst influenza season in recent years. Public hospitals faced shortage of manpower due to surge in hospital admissions. The Hospital Authority (HA), which was heavily under fire at that time due to poor allocation of resources, announced suspension of all hospital accreditation activities to alleviate non-clinical duties of healthcare staff. They also tried to employ part-time doctors and nurses to try to secure more manpower, and borrowing beds from private hospitals.

Due to the unusual surge in service demand, some of the internet users in Mainland China even spread rumours claiming the summer flu in Hong Kong is comparable to SARS in 2003. Following the incident, Secretary for Food and Health, Professor Sophia Chan has quickly clarified that the summer flu is totally incomparable to the SARS outbreak, with its mortality rate staying around 2.1%, a figure comparable to winter or summer influenza seasons over the past few years.

Summer flu is not rare in Hong Kong but it was stronger in 2017
Summer flu is not rare in Hong Kong but it was stronger in 2017

The summer influenza season eventually ended in August. "Hong Kong entered the summer influenza season in mid-May, which is earlier than the past seasons that usually occurred from July to September. The seasonal influenza (SI) activity increased steadily in June and rose sharply to a very high level in mid-July with some surveillance parameters surpassing their highest levels in recent years. It decreased notably in early August and returned to a baseline level in late August," a spokesman for the CHP said.

During the summer influenza season, a total of 576 adult cases of influenza-associated admission to the Intensive Care Unit or death (including 428 deaths) were recorded from May 5 to August 29. In children, in the same period, 19 cases of severe influenza-associated complication or death (three deaths) were detected. MIMS

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