Influenza on the increase in Norway

We expect that infection caused by A (H1N1) virus (swine influenza) could constitute a larger proportion of this winter's epidemic than in the last two winters, but that pre-existing immunity in the population will limit the epidemic's spread. This year we have a regular seasonal epidemic, not a pandemic. A pandemic requires a new virus to which people do not have immunity, which is not the case this year.

"Influenza epidemics are unpredictable. The Norwegian Institute of Public Health is monitoring the situation closely with the means at our disposal. The number of people who become ill varies from year to year. The size of the epidemic is impossible to predict," says Karin Rønning, Director of the Department of Infectious Disease Surveillance, at the Norwegian Institute of Public Health.

It is expected that, as with any influenza outbreak, some people will be admitted to hospital, including intensive care, and that some deaths will occur. This is not specifically caused by the A (H1N1) virus, but can happen as a result of any influenza infection.

The risk of serious illness

For most people, influenza is a disease that passes without the need for medical attention.

People with risk factors are most vulnerable to severe illness, and it is rare for healthy people to develop serious complications from influenza. People with risk factors may also experience deterioration of their underlying disease following influenza. The risk groups apply for all types of influenza virus.

Life-threatening illness rarely occurs in healthy people. Death may also occur, but mainly among people who are at increased risk for severe illness.

People with risk factors should be vaccinated as soon as possible. The risk groups are:

• people who are 65 years or older 
• residents in sheltered housing and nursing homes 
• pregnant women, especially in the 2nd and 3rd trimester 
• adults and children with chronic respiratory diseases, particularly those with reduced lung capacity 
• adults and children with chronic cardiovascular disease, especially those with severe heart failure, low cardiac output or pulmonary hypertension 
• adults and children with impaired immunity against infection 
• adults and children with diabetes mellitus (both type 1 and type 2) 
• adults and children with chronic renal failure 
• adults and children with chronic liver failure 
• adults and children with chronic neurological disease or injury 
• adults and children with very severe obesity, i.e. body mass index (BMI) over 40 kg/m2 

Vaccination is also recommended to health care personnel as they are more susceptible to infection from patients and risk infecting other patients if they are become ill.

Protection

Rare cases of life-threatening illness can occur with all the three circulating influenza viruses, but these have been somewhat more frequent in adolescents and young adults with A (H1N1) virus (swine influenza).

Norwegians are generally well protected against A (H1N1) by the pandemic, because so many people either took the vaccine or became ill. However, the efficacy of the vaccine from 2009 is no longer sufficient for many people to prevent disease, and if you are in a risk group you should take the seasonal vaccine even if you had the pandemic vaccine.

Admission to hospital

Every year, influenza viruses cause outbreaks of influenza. During this period, the primary health service and hospitals receive a greater number of patients.

The Norwegian Institute of Public Health does not have a surveillance system of influenza-related hospital admissions. We want to establish this to give a better overview of severe illness from influenza.

Together with influenza, a number of other respiratory viruses (e.g. RS-virus) are circulating which present a similar clinical picture to influenza, leading to many hospital admissions. Many patients with poor lung function (COPD and asthma) are admitted to hospital, some due to influenza and others due to other circulating respiratory viruses.

Treatment

Use of antiviral drugs may be considered, especially for the risk groups and where there is evidence of severe illness. Treatment should start within 48 hours of the onset of symptoms.

Vaccination autumn 2012

The vaccination coverage of risk groups is lower in Norway than in many other European countries, and is significantly lower than the target of 75 per cent recommended by the World Health Organization.

For the 2012-2013 season, the NIPH despatched 412,000 doses of seasonal influenza vaccine to municipalities for use in risk groups. In addition, around 20,000 doses of vaccine were despatched for use in non-risk groups. As of 30th November 2012, other wholesalers had sold about 34,000 doses.

It is uncertain how many of the despatched doses have been administered. As of 30th December 2012, there were 62,892 registered influenza vaccinations in SYSVAK.

Informal reports from the municipal health service indicate that interest in the influenza vaccine has been low in autumn 2012. There is reason to believe that many municipalities still have available vaccine doses intended for the risk groups.

There is a shortage of available influenza vaccines in Europe. The Norwegian Institute of Public Health is investigating the possibility of obtaining more vaccine for the 2012-2013 season.

Provided by Norwegian Institute of Public Health