A WHO’s Who of Human Flu

9 February 2011 (Last Updated February 9th, 2011 18:30)

The 2009 H1N1 pandemic may be over, but various strains of influenza are still present. Sarah Blackman finds out from the World Health Organisation (WHO) and other industry experts what surveillance systems are being used to track the disease and prevent further hospital admissions.

A WHO’s Who of Human Flu

Hospital management teams around the globe were able to breathe a little easier when the World Health Organisation (WHO) declared an end to the deadly H1N1 2009 pandemic. More recently, the Health Protection Agency (HPA) in the UK announced that new cases of flu have fallen dramatically. But still, the disease lingers and cannot be wiped out.

It is important to note, however, that the movement of influenza can be controlled. Whereas years ago the virus could obliterate an entire nation, the healthcare industry now has the technology and the know-how to track, monitor and weaken the disease.

Surveillance

Copious amounts of research into how influenza produces disease and how it circulates from human to human, or indeed from animal to human and vice versa, have led to the development of countermeasures to prevent the spread of flu strains, be they old or new. The bulk of the clinical observation and laboratory diagnosis is being carried out by a global network of WHO collaborating centres for influenza.

The WHO Influenza Centre at the National Institution of Medical Research in the UK is one of five WHO collaborating centres for reference and research on influenza, which aim to detect the emergence of novel influenza subtypes with the potential to cause a pandemic.

Such subtypes include the influenza A virus H5N1, which passed from birds to humans in 1997 during an outbreak of avian flu among poultry in Hong Kong, and the avian H9N2 viruses that caused human infections in 1999 and 2003.

"New cases of flu have fallen dramatically, but the disease still lingers and cannot be wiped out."

The H1N1 2009 subtype, more commonly known as swine flu, which by the end of February 2010 caused 15,921 deaths worldwide, was first detected in Mexico, and laboratory testing at centres of disease and control (CDC) in the US later confirmed that the disease was circulating among humans in California. A spokesperson for the organisation explains: "Usually with any flu outbreak, local health departments do a standard typing to determine the flu strain they are dealing with. In the case of the H1N1 outbreak last year, the typing did not match any known strains. For this reason, the CDC was contacted."

The CDC has a series of emerging infection sites located around the US providing test results that enable it to develop a strong statistical sampling base, key to tracking flu.

Meanwhile, across the Pacific, the Australian Sentinel Practices Research Network (ASPREN) works to collect de-identified information on influenza-like illnesses seen in general practice with the support of the Royal Australian College of General Practitioners. Other life-saving systems, used to detect the viruses in Australia, include FluTracking, an online health surveillance system, and the National Notifiable Diseases Surveillance System.

In the UK the HPA gathers samples from GP surgeries and hospitals to monitor the circulation of flu viruses. Professor John Watson, head of the organisation's respiratory diseases department, explains: "These samples are sent to the HPA's network of regional labs for a provisional analysis of flu and then on to the HPA's Respiratory Virus Unit in Colindale for full virus characterisation. The lab tests for susceptibility and performs a full genome analysis."

Infections are also tracked by QSurveillance, a collaborative project involving the HPA, Egton Medical Information Systems (EMIS) and the University of Nottingham's Division of Primary Care. The database receives information from around 3,300 general practices every day, covering a population of around 24 million patients. This data is reported to the HPA and forms a critical part of the UK emergency response to a pandemic.

So what constitutes a pandemic? According to the WHO it can be defined as a community-wide spread of a novel disease in at least three countries, one of which cannot be in the same WHO region as the others.

To prevent such an occurrence, the spread of influenza not only has to be monitored, it must also be controlled.

Vaccination

The most effective way of controlling the spread of flu is through vaccination, and, twice a year, the WHO advises on which strains should be included in the seasonal trivalent vaccine to give the best protection.

The vaccine will always contain a H1, H3 and B strain of virus, according to Watson. For example, the 2010-2011 flu vaccine was matched to those strains that are currently circulating, namely A:H3N2, B and 2009 H1N1.

"Twice a year, the WHO advises on which strains should be included in the seasonal trivalent flu vaccine."

These vaccines have been effective. However, some organisations are calling for an increase in immunisation rates. In a letter issued in June, the UK Department of Health said, "Although there has been progress in the uptake of seasonal influenza vaccine in healthcare workers this year (seasonal influenza vaccine uptake increased from 16.5% last year to 26.4% and the swine influenza vaccine uptake was 40.4%), we need to see further improvement in increasing their immunisation rates."

The department said it will work with the National Health Service to help healthcare workers understand the importance of being vaccinated to protect themselves, their patients and their families.

The CDC is also encouraging those at high risk of flu complications (pregnant women, over 65s and children under five years old) to be immunised.

The problem with vaccines, however, is that the WHO must prepare the formulation of ingredients almost a year in advance of when the flu will actually hit, explains Gregory Härtl, the WHO's global alert and response team leader for communications. "For the northern hemisphere, the meeting is in February to prepare vaccines in time for the next winter," he says.

But, how can we prepare for new strains before they even exist? Unfortunately, there isn't an answer to this question. The only thing we know for sure is that flu is unpredictable and that when it hits, the healthcare industry must be prepared to stop the disease in its tracks.