Lessons learned from the first wave of the swine flu pandemic

A legacy of influenza associated with the 2009 pandemic virus is likely to be with us for many years to come, John Manos reports.

On this page:
Vulnerable groups, resistant strains
Pandemics don't just come and go
Carte blanche for self-certified absence?.

The keynote speaker at the IRS conference "Surviving pandemic flu in the workplace"¹ - Jonathan Van-Tam, professor of health protection at Nottingham University - described the experience outside the UK of the first wave of the 2009 pandemic. While the timing, scale and duration of the second wave were "unknowns", he said, the experience of Mexico - and of Australia and New Zealand, where the first wave outside central and north America was most severely felt - were important.

The epidemiology of the early weeks of the outbreak in Mexico had provided important information about which sections of the population as a whole are being affected by the pandemic H1N1 2009 virus; similarly, while the first wave had been mild in the northern hemisphere, crucial information was emerging from the southern hemisphere's winter experience.

Analysis of Mexican data showed a clear age-specific gradient in the percentage of confirmed cases - with the chances of being infected declining with age. This is consistent with the evidence that, among those alive today, there is a legacy of resistance to the 2009 virus among those who were exposed to the 1968 pandemic. At the same time, the Mexican data showed that, among those infected, the likelihood of death showed an age-specific gradient in the opposite direction - ie, the case fatality rate rose with age. The paradox associated with the 2009 pandemic therefore is, Van-Tam said: "You are much less likely to be infected at all, the older you get; but if you do get infected and you are old, you have a higher chance of not doing so well out of it." Despite this, overall, pandemic deaths in Mexico were fairly evenly spread across the age spectrum. Many deaths did occur in young people and working-age adults.

These facts were important for HR planning and the assessment of the impact of the pandemic on workforces. "While there have been an extremely small number of deaths, there will be deaths among young adults this autumn, as there have been already, and we will see the distribution of disease spread across the whole age spectrum, including among younger workers," Van-Tam said.

Van-Tam presented data illustrating the greater impact of the pandemic first wave in Australia, during the June/July winter months, and the lessons for the UK. "What we saw in June and July [in the UK] was the virus having to work hard against the nice sunny conditions and against the closing of schools [that helped mitigate the spread of the virus]. We are now entering the autumn period when the virus and the season will be working together and the schools will be open - a very different picture."

The New Zealand first wave experience also helped further characterise the 2009 virus. For example, the rate of notification of new cases of H1N1 flu in New Zealand peaked at the same time as the rate of hospitalisations peaked (in week 28 of 2009). This showed that, for the most part, people were being hospitalised as a direct result of catching swine flu, said Van-Tam, rather than hospitalisation occurring some weeks after infection as a result of complications such as bacterial pneumonia, which has been characteristic of seasonal flu and earlier pandemics.

Hospitalisations in the southern hemisphere, like deaths, were spread across the age spectrum, but there were definite peaks among very young children (less than one year of age), and young adults of working age, in contrast to the usual situation with seasonal flu.

Vulnerable groups, resistant strains

The unexpected mildness of the 2009 pandemic worldwide was a significant surprise, the overall case fatality rate in the southern hemisphere being very low, between 0.1% and 0.2%. Even though the clinical attack rate in Mexico was as high as 40% in the first wave, the indications were that it would be lower in the second. As a result, there was a risk of complacency among employers who may consider that the risk has been exaggerated, Van-Tam said. He cautioned against this, saying: "We really do not know what is going to happen this winter."

In the UK, hospitalisations have been between 1% and 2% to date but there has been an unusually high proportion requiring intensive care facilities, Van-Tam noted, perhaps as high as 10% of all hospitalisations.

As far as the greatest risk of death or hospitalisation were concerned, clearly those with underlying health conditions were at risk; and there were also "strong signals" that pregnant women and asthmatics (ie those relying on inhalers or similar treatments) were also at higher risk. Evidence (from north America) also implicated morbid obesity as a significant risk factor. Nevertheless, it had to be remembered, Van-Tam stressed, that 20% of deaths in the UK had been in previously healthy people.

Regarding patterns of resistance to the antiviral drug Tamiflu, for which there had been some concern in the past, there was little evidence that this was emerging to a significant degree, Van-Tam said. However, there was evidence that widespread use of the drug for prophylaxis (ie preventing infection among those who have been exposed to the virus) should be discontinued, to minimise the generation of resistant strains of H1N1, and that those organisations planning such use should reconsider their policy.

Pandemics don't just come and go

Whatever the scale of the 2009/10 second wave, we are likely to see significant seasonal outbreaks of this strain for some years to come. It should be remembered that the H3N1 seasonal winter flu virus is a distant relative of the 1968 pandemic virus that continues to circulate today. "We should not imagine that the problems of the 2009 swine flu virus will all be over by the spring," said Van-Tam.

Carte blanche for self-certified absence?

An employment law specialist speaking at the IRS event also considered the implications of widespread pandemic flu illness on absence management procedures, considering such questions as: to what extent are employees entitled to absent themselves because of concern about risks of infection, or for the purposes of unscheduled childcare responsibilities? Kate Hodgkiss, of the employment lawyers DLA Piper, said there was "no carte blanche for pandemic-related absence", but she stressed that there were dangers for employers who do not accept applications for leave on the grounds of fear of infection while travelling to work on public transport or through contact with colleagues; or for extended leave to care for children or dependent relatives. Resistance to (or refusal of) such requests may create, in itself, automatic grounds for a claim of unfair dismissal.

Clearly the vulnerability of pregnant women to complications arising from infection meant that special consideration had to be given to them. But in other cases, Hodgkiss said, it should be remembered that the emergency time-off provisions of employment legislation do not preclude an employer refusing paid time off and requiring that absence be taken from leave entitlement. Similarly, the provisions providing for time off to care for a sick relative, or a child excluded from school, do not bestow a right to unlimited time off; the intention of the provisions is, she pointed out: "to allow, in an emergency, an employee to take time off to put in place special arrangements".

1. IRS conferences, "Surviving pandemic flu in the workplace", 6 October 2009, St Ermins Hotel, London.