Fears swine flu is ‘silently spreading’ after first UK case – as people with cold symptoms told ‘stay at home’

SWINE flu is likely already spreading in UK undetected, experts have warned.

It comes after a Brit fell ill with a new strain of the disease, dubbed H1N2.

The patient from Yorkshire only experienced mild cold-like symptoms and has since recovered.

The virus was spotted during routine flu surveillance, making it unlikely to be the only infection, according to Dr Phillip Gould, a virologist from Coventry University.

He told The Sun: "It's highly likely there are more cases [of swine flu] in the UK, that haven't been picked up yet."

Only a handful of patients who see their GP with respiratory symptoms, like a runny nose and cough, get sent on for testing.

This means the chance of the Yorkshire case being the only infection is "pretty small", Dr Phillip said.

The UK Health Security Agency (UKHSA) is working rapidly to trace contacts and find the source of the infection, with the patient not thought to have had close contact with pigs.

As surveillance ramps up, there is a chance that more cases could emerge in the coming weeks, the expert said.

"While they test people the patient has come into contact with and monitor local hospitals in the area more cases could be found," he explained.

Professor Francois Balloux, an epidemiologist from University College London, also said the singular case "may indicate circulation in humans" and requires "further monitoring".

There have been 50 human cases of H1N2 reported globally since 2005.

But none of them are related genetically to this strain seen in the UK.

Swine flu can be passed from pigs to humans via direct contact, but only in rare cases spreads between humans. 

"Not every new agent is a threat"

Professor Ian Jones, a virologist at the University of Reading, said the fact more cases might emerge is not necessarily a cause for concern.

He said: "Although a single case may not be representative, the fact the individual concerned had a mild infection that resolved without hospitalisation is also in keeping with previous experience.

“We should remember that surveillance programmes can discover infections that might never have been noticed based on case numbers or severity, so reasoned tolerance has to be applied. Not every new agent is a threat.”

Dr Phillip added: "Swine flu is designed to spread in pigs, so chances are it won't be very good at replicating in humans and won't cause such serious disease."

The UKHSA's advice for all respiratory symptoms remains the same - avoid contact with others and stay home while they persist, particularly if they are old or have existing medical conditions.

Swine flu can be passed from pigs to humans via direct contact, but only in rare cases spreads between humans. 

In 2009, there was a pandemic in humans caused by flu strain H1N1, commonly referred to as swine flu.

The H1N1 strain was first detected in April of that year in North Amercia but quickly spread across the US and worldwide.

By the time the WHO declared it a pandemic in June 2009, it had spread to 74 countries and territories.

It killed 457 people in the UK. But it now circulates in humans seasonally, is included in the flu jab, and is not referred to as 'swine flu'.

The WHO declared the pandemic was over in August 2010.