Hong Kong Girds For More Flu

HK’s recent history of `Twin Peaks’ of influenza– Credit Flu Express

 

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Although there are some subtle signs that the worst of Hong Kong’s severe flu season may be waning, school and work schedules are just now returning to normal following the Lunar New Year Holiday, and concerns run high that a second surge of flu may ensue.

With 310 flu-related deaths recorded since early January, this year’s flu outbreak is already more than twice as deadly as last year, with the potential for seeing several more months of activity. 

Complicating the situation, Hong Kong often sees a biphasic or `double peaked’  flu season, as the chart at the top of this post , and the following 2008 PLoS One research paper illustrates:

 

Seasonality of Influenza A(H3N2) Virus: A Hong Kong Perspective (1997–2006)

Julian W. Tang,^1,* Karry L. K. Ngai,¹ Wai Y. Lam,¹ and Paul K. S. Chan^1,2

(EXCERPT)

Hong Kong is a subtropical region of almost 7 million people, 95% of whom are ethnic Chinese, with a mean temperature of 24°C and mean relative humidity of 79% [27]. It lies geographically in the Northern hemisphere, and its influenza season occurs during February–April, sometimes with a second peak during June–August, each year.

In contrast, other Northern hemisphere countries usually have a more extended influenza season from November to March/April, whereas the influenza season of Southern hemisphere countries usually occur from May to September [7], [28].

Hence, Hong Kong may be unique in that its biphasic influenza seasonality seems to straddle those of the Northern and Southern hemisphere countries, making the molecular epidemiology of its circulating influenza viruses of great interest. In addition, Hong Kong and Southern China have been referred to as the ‘epicenter’ for new influenza A viruses with pandemic potential for over 25 years now [29]. For all of these reasons, any investigation of the underlying basis for influenza seasonality may benefit greatly from a study of influenza viruses isolated from Hong Kong.

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Hong Kong officials are worried enough they are making special arrangements to purchase a quantity of the recently revised Southern Hemisphere vaccine for use in a second wave of vaccination for high risk individuals, as announced recently in New flu vaccine ready by April.

This update from Hong Kong’s CHP.

 

Latest update of surveillance data in winter influenza season

The Centre for Health Protection (CHP) of the Department of Health today (March 2) reported the latest surveillance data of the winter influenza season, and again urged the public to heighten vigilance and get vaccinated early against seasonal influenza.

"As most schools resumed after the Lunar New Year, we today issued letters to kindergartens, child care centres and primary and secondary schools as well as special schools to alert them to the current influenza activity, which remains at a high level and is expected to remain so for some time. Continued vigilance is warranted," a spokesman for the CHP said.

Schools should continue to actively check the body temperature of all students every day to identify those with fever who should not attend school till 48 hours after it subsides. Staff with respiratory illnesses should also refrain from work," the spokesman added.

Schools may refer to the CHP's Guidelines on Prevention of Communicable Diseases (LINK) for further information.

Regarding severe cases, from noon yesterday (March 1) to noon today, six additional cases of influenza-associated admission to intensive care units or death (including three deaths) among adults aged 18 or above have been recorded under the enhanced surveillance in collaboration with public and private hospitals reactivated since January 2 and an additional death was recorded among previously reported cases, bringing the total to 421 (310 deaths) so far. Among them, 403 were A(H3N2), two were A(H1N1)pdm09, seven were A pending subtype and nine were B. In the last winter season in early 2014, 266 (133 deaths) were filed.

Meanwhile, no additional cases of severe paediatric influenza-associated complication or death among children aged under 18 have been reported since yesterday via the ongoing reporting system and the total this year hence remains at 17 (one death) and all were A(H3N2). In 2014, 27 cases (four deaths) were filed.

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Although the two viruses aren’t really comparable, this year’s seasonal flu death toll has now exceeded the number killed in Hong Kong by SARS (n=299)  in 2003 (see SARS and Remembrance).

 

The difference being that SARS infected fewer than 2000 people in Hong Kong while racking up that toll, while influenza has likely infected hundreds of thousands.

 

While other areas in Europe, India, and Asia are seeing high levels of seasonal influenza activity right now,  we always pay special attention to Hong Kong’s flu season. Simply because it has excellent surveillance, and its proximity to southern China makes its a credible place to look for the emergence and spread of novel flu viruses.

CDC: Early Data Suggests Potentially Severe Flu Season

 

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As follow up to this morning’s blog (see CDC HAN Advisory On `Drifted’ H3N2 Seasonal Flu Virus), and a blog I wrote a month ago called A `Drift’ In A Sea Of Influenza Viruses, we’ve got a press release from the CDC warning that there are early signs that might indicate a rough flu season ahead.

Earlier today CDC Director Dr. Thomas Frieden and Dr. Joseph Bresee held a teleconference, where they went over last night’s HAN announcement, and discussed the recent influx of a newly `drifted’ H3N2 virus not well covered by the current vaccine. 

 

Since vaccine strain selections must be made 6 months before the start of each flu season, there’s always a chance that one or more of the viruses in circulation will drift away from the vaccine.  This constant evolution of influenza viruses is illustrated quite nicely in the NIAID video Influenza: Get the (Antigenic) Drift.

 

A transcript of today’s briefing and audio file should be posted on the CDC’s media website  later today or tomorrow. In the meantime, we’ve the following press release:

 

Early Data Suggests Potentially Severe Flu Season

CDC Urges Vaccination, Treatment

 

For Immediate Release: Thursday, December 4
Contact: Media Relations
(404) 639-3286

Early data suggests that the current 2014-2015 flu season could be severe. The Centers for Disease Control and Prevention (CDC) urges immediate vaccination for anyone still unvaccinated this season and recommends prompt treatment with antiviral drugs for people at high risk of complications who develop flu.

So far this year, seasonal influenza A H3N2 viruses have been most common. There often are more severe flu illnesses, hospitalizations, and deaths during seasons when these viruses predominate. For example, H3N2 viruses were predominant during the 2012-2013, 2007-2008, and 2003-2004 seasons, the three seasons with the highest mortality levels in the past decade. All were characterized as “moderately severe.”

Increasing the risk of a severe flu season is the finding that roughly half of the H3N2 viruses analyzed are drift variants: viruses with antigenic or genetic changes that make them different from that season’s vaccine virus. This means the vaccine’s ability to protect against those viruses may be reduced, although vaccinated people may have a milder illness if they do become infected. During the 2007-2008 flu season, the predominant H3N2 virus was a drift variant yet the vaccine had an overall efficacy of 37 percent and 42 percent against H3N2 viruses.

“It’s too early to say for sure that this will be a severe flu season, but Americans should be prepared,” said CDC director Tom Frieden, M.D., M.P.H. “We can save lives with a three-pronged effort to fight the flu: vaccination, prompt treatment for people at high risk of complications, and preventive health measures, such as staying home when you’re sick, to reduce flu spread.”

Depending on the formulation, flu vaccines protect against three or four different flu viruses. Even during a season when the vaccine is only partially protective against one flu virus, it can protect against the others.

“While the vaccine’s ability to protect against drifted H3N2 viruses this season may be reduced, we are still strongly recommending vaccination,” said Joseph Bresee, M.D., Chief of the Influenza Epidemiology and Prevention Branch at CDC. “Vaccination has been found to provide some protection against drifted viruses in past seasons. Also, vaccination will offer protection against other flu viruses that may become more common later in the season.”

Influenza viruses are constantly changing. The drifted H3N2 viruses were first detected in late March 2014, after World Health Organization (WHO) recommendations for the 2014-2015 Northern Hemisphere vaccine had been made in mid-February. At that time, a very small number of these viruses had been found among the thousands of specimens that had been collected and tested.

A committee of experts must pick which viruses to include in the vaccine many months in advance in order for vaccine to be produced and delivered in time for the upcoming flu season. There is always the possibility that viruses will drift during that time.

Influenza activity is currently low in the United States as a whole, but is increasing in parts of the country. “We are just at the beginning of the season. It’s not too late to get your vaccine,” Dr. Frieden says.

Influenza antiviral drugs – Tamiflu (oseltamivir) and Relenza (zanamivir) can reduce severe complications such as hospitalization and potentially death for people who are at high risk of serious flu complications or are very sick. Treatment of high risk patients should begin as soon after symptoms develop as possible, without waiting for lab tests to confirm flu infection.

Those at high risk from influenza include children younger than 5 years (especially those younger than 2 years); adults 65 years and older; pregnant women; and people with certain chronic health conditions such as asthma, diabetes, heart or lung disease, and kidney disease.

CDC recommends that people at high risk check with their doctor or other health care professional promptly if they get flu symptoms. Studies show that flu antiviral drugs work best for treatment when they are started in the first 48 hours after symptoms appear. Flu symptoms can include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue.