Europe may be blind to swine flu cases

A doctor performs a swab test, to test the patient for H1N1. At present, only high-risk patients are being tested in Europe (Image: Burger / Phanie / Rex Features)

Editorial: Ignoring flu won't make it go away

EUROPE might have more H1N1 swine flu than it knows. The virus could be circulating widely but not being spotted simply because people are not being tested.

• 20 May 2009 by Debora MacKenzie
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As New Scientist went to press, the World Health Organization was still undecided about declaring a full-blown pandemic, despite a surge in swine flu cases in Japan. To do this it needs evidence of "sustained transmission" outside the Americas, where the virus originated. This means finding cases in the general population that have not had known contact with places or people confirmed to have the virus. Japan found H1N1 this week in over 100 people, many without known contact.

But European countries are using a case definition from the European Centre for Disease Prevention and Control (ECDC) in Stockholm, Sweden, that virtually precludes discovering such cases. It recommends testing people with symptoms only if they have been to affected countries or had contact with a known or suspected case in the past seven days.

"We can't test every mild case of flu symptoms," says Johan Giesecke, chief scientist at ECDC. "But it's true, we might not be seeing community spread because we aren't looking." On 18 May, the UK had 101 confirmed cases of H1N1, of which only three fell outside the case definition.

The UK Health Protection Agency's criteria are similar (see diagram). Doctors "are encouraged to use this algorithm", an HPA spokesperson told New Scientist, but they can "use their clinical discretion" to test anyone.

An anonymous UK New Scientist reader, and two family members, had flu symptoms after one returned ill from New York on 10 April. They were not tested for H1N1. "My general practitioner is horrified that I am not even eligible for a test because I have not returned from Mexico in the last seven days, nor been in contact with someone who has been diagnosed."

A New Scientist reader had flu symptoms on returning from New York but was not tested for H1N1

Tests may simply be unavailable. "I was given only two swabs [for H1N1] initially," says Laurence Buckman, head of the GP committee of the British Medical Association. More are available now, "but if you can't do many tests you save them for people who meet the case definition".

Any others, says Buckman, will be picked up by "sentinel" clinics that compile weekly statistics. The ECDC claims this system "would detect circulation of the new H1N1 virus before any major outbreaks occur".

However, such sentinel systems are designed to track ordinary flu, not to detect a new infection that is initially highly localised. "It may take weeks before the numbers indicate an epidemic," warns Dick Wenzel of Virginia Commonwealth University in Richmond, past president of the International Society for Infectious Diseases. He advises testing clusters of flu and all severe cases.

Hong Kong is testing all hospitalised cases of flu and pneumonia. Belgium, departing from ECDC advice, is testing flu-like clusters and deaths. But without more tests, Europe may be missing an epidemic.

Editorial: Ignoring flu won't make it go away