Ministry of Health warning on influenza outbreak

Ministry of Health warning on influenza outbreak

The Ministry of Health is advising parental vigilance as a seasonal influenza outbreak continues to affect school-age children.

Director of Public Health Dr Mark Jacobs said today that the current rate of influenza in New Zealand communities was higher than at the same time last year, and tests had confirmed influenza B viruses were dominant.

Influenza B is more commonly associated with infection outbreaks among school-age children than older age groups and many schools around the country recently reported high levels of pupil absenteeism.

So far, there have been more influenza B Hong Kong infections than the B Shanghai virus, which is also circulating in the community.

``People who were vaccinated last year are likely to have some remaining protection against the B Hong Kong strain. It's possible children may not have been exposed to this particular influenza B strain, which is why there has been such an impact in various schools around the country,'' Dr Jacobs said.

``Because the current influenza outbreak this season is in children, they are more at risk of getting the secondary complications of influenza, including bacterial infections like ear infections or pneumonia.

``That's why it's important we keep a close eye on children sick with flu-like symptoms. If children are unwell they should be kept at home from school with a parent or responsible guardian.''

The Ministry also advises that sick children should be kept warm, given paracetamol for fever and plenty of fluids. If the child is not getting better, gets better and then develops another fever, or is having breathing difficulties, the child should be taken to a GP. If possible, parents should ring their medical centre before going in, so staff can take steps to minimise the spread to others.

If parents have already taken their child to a doctor and had a diagnosis of influenza, but they are concerned about their child or the child gets sicker, then parents are advised to take the child back to the doctor, as they may have developed a secondary infection.

``Influenza B outbreaks are generally less severe than influenza A, but any influenza infection can be very unpleasant and young people can become unwell very quickly. It is important to remember that being fit, active or healthy does not protect against influenza. It's highly contagious and anyone can catch it. ''

The influenza B viruses circulating this year, particularly in Auckland and Wellington schools, are predominantly the Influenza B Hong Kong strain and a few of the Influenza B Shanghai strain. The B Shanghai virus is in the influenza vaccine this year after the Shanghai virus circulated in 2004. While the B Hong Kong strain was in the 2004 vaccine, it is not in this year's vaccine.

Children with high-risk conditions are encouraged to have influenza vaccine and are funded under the Ministry of Health's subsidised influenza vaccination campaign.

The influenza vaccine is also available for children and adults who do not have high-risk conditions, but it is not publicly funded.

The subsidised influenza vaccination campaign for high-risk New Zealanders -- people aged 65 and over, as well as adults and children with long-term health conditions such as heart disease, stroke and diabetes -- runs until the end of July.

Dr Jacobs said the annual influenza immunisation is the best form of defence against the disease, and he strongly urged people to get immunised, particularly those who are most vulnerable and in the at-risk groups . These people are at higher risk of developing complications from an influenza infection.

So far, more people eligible for free influenza immunisation have been vaccinated than last year. There were 436,600 vaccine doses sent to GPs to the end of May this year, compared with 323,699 doses sent out at the same time last year.

There are 460,560 people aged 65 and over who are eligible for the free vaccine. As well as this, it is estimated there are around 254,000 in the 16 to 64-year age group who will qualify for free influenza vaccinations.

ENDS

Background

Influenza activity in New Zealand peaked last year at the end of September, a month later than the peak in 2003 and 2002.

The three influenza strains in this year's vaccine are:

A/Wellington/2004 (H3N2)

A/New Caledonia/1999 (H1N1), and

B/Shanghai/2002.

Influenza B

It is well-documented that influenza B predominates or co-dominates every second year in the southern hemisphere. This happened in New Zealand in 1991, 1993, 1995, 1997 and 2001. The last significant year for influenza B in New Zealand was 2001.

In 2005, influenza B circulation has three interesting features:
1) Influenza B became the predominant strain at the beginning of the influenza season. This is in contrast to the usual pattern that influenza B predominates at the tailing period of the season.
2) B/HongKong lineage virus and B/Shanghai lineage virus are co-circulating in the community, and both of these strains caused school outbreaks in the Auckland and Wellington regions.
3) So far, there have been more B/HongKong lineage viruses (12) than B/Shanghai lineage viruses (10).

In October 2004, the Australian Influenza Vaccine Committee (AIVC) made influenza vaccine composition recommendations for 2005 for New Zealand, Australia and South Africa.

B/Shanghai/361/2002-like strain was chosen as the B component of the vaccine based on epidemiological, antigenic, genetic and serological evidence. The great majority of influenza B isolates was antigenically closely related to B/Shanghai/361/2002-like strains. In 2004, B/Shanghai lineage viruses were the predominant influenza B viruses whereas B/Hong Kong lineage viruses circulated at a lower level.

Because influenza B has a greater antigenic stability than influenza A, illness due to influenza B tends to occur mostly in younger age group, particularly school-age children. ie older populations have immunity from previous infection or vaccination. This explains why children are affected in the current school outbreaks in the Auckland and Wellington regions. In general, influenza B causes less severe diseases compared with influenza A. For example, it has been reported the frequency of serious influenza B infection requiring hospitalisation is about 4-fold less than that of influenza A virus. In addition to the usual influenza-like symptoms, gastrointestinal symptoms and muscle inflammation (Myositis) are seen more often in influenza B than influenza A.

Influenza infection control in schools
The key measures to limit the spread of influenza or other highly infectious viruses in schools are:

Cover coughs with a tissue and not hands.

Wash hands – after going to the toilet, and before eating and preparing food. Schools should ensure that good hand-washing and drying facilities are available.

Keep children away from school if they are unwell with flu-like symptoms or gastroenteritis.

For further information on circulating influenza strains please refer to the ESR website: http://www.surv.esr.cri.nz/virology/virology.php

Questions and Answers
What is influenza?
Influenza is a serious illness that in New Zealand usually causes epidemics every year during the winter months. The illness comes on suddenly with a fever, sore throat, dry cough, aches and pains and headaches. People feel very unwell and the elderly and chronically ill can develop pneumonia and other problems. They may need hospital care.

Why do people need to vaccinate against influenza?
Influenza immunisation is the best protection against influenza. Influenza infection in people with ongoing medical conditions, even if their condition is well controlled, may lead to more serious illness and death.

Influenza can cause pneumonia and can act as a trigger that makes existing medical conditions worse. In older people and those with ongoing medical conditions such as heart disease, other respiratory problems and diabetes this can lead to hospitalisation and even death.

Where can eligible people get a free vaccination?
Free vaccinations are available from your local General Practitioner even though a practice nurse may be the one who actually administers the injection to you. The vaccine is injected into your upper arm.

How can I tell the difference between a cold and influenza?
Influenza makes people feel miserable and is much more serious that a common cold. Influenza will leave you ill for up to 10 days. Most people suffer from a high fever and may require bed rest. Some may also have shivering attacks, muscular pains, headaches, a dry cough, possible vomiting and complications like pneumonia can follow. A vaccine is available to protect against influenza.

A cold however has much less severe symptoms and they generally last only 2-4 days. High fever is less common and shivering attacks and severe headaches are rare. Muscular pains and vomiting are infrequent and the cough will be less severe. There is no vaccine available.

How safe is the vaccine?
The immunisation will not give you influenza because the vaccine contains disrupted virus. Most people have no reaction to the injection. Occasionally the place where the injection was given is red or sore. Some people may feel unwell for a day or two. These are normal responses to the immunisation.

Does the vaccine actually work?
Yes. For those at high risk, influenza vaccination reduces hospitalisation by 50 percent and mortality by 70 percent. In general the vaccine is 70-90 percent effective in preventing influenza in healthy adults.

Will I get influenza from the vaccination?
No. Influenza vaccine cannot give you the 'flu as it contains fragments of disrupted virus.

Summary of 2004 influenza statistics
During the 2004 influenza season, 3277 consultations for influenza-like illness were reported from a national sentinel network of 86 general practices. It is estimated that influenza-like illness affected more than 35,000 New Zealanders during the season, compared with more than 46,000 people in 2003.

How are the statistics collected?
There are two parts to the influenza surveillance systems in New Zealand - sentinel general practice (GP) surveillance and laboratory-based (mainly hospital) virological surveillance.

General Practice Surveillance
The sentinel GP surveillance system started in 1991 as part of the WHO Global programme for influenza surveillance. It is operated nationally by ESR and locally by influenza surveillance co-ordinators in the public health services.

In 2004, national influenza GP surveillance was carried out from May to October. Local surveillance co-ordinators recruited General Practices within their region to participate on a voluntary basis. GPs recorded the number of consultations for influenza-like illness each week and the age group of each of these suspected cases.

Each practice was also asked to collect throat or nose swabs from patients seen with an influenza like illness each week. The swabs were sent to a regional virus diagnostic laboratory and/or ESR for strain identification.

Laboratory-based surveillance (year round)
In addition to positive identification of the influenza virus from GP surveillance, year round virological surveillance of influenza (and other viruses) is carried out by the four regional virus diagnostic laboratories at Auckland, Waikato, Christchurch and Dunedin hospitals, and by ESR. ESR acts as New Zealand's designated WHO National Influenza Centre.

Each week the regional virus diagnostic laboratories report all viral identifications including influenza largely from hospital in-patients and outpatients, to ESR, where the data is collated and reported nationally.

ENDS

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