Great tits are being severely affected by a new strain of avian pox in Britain that "significantly reduces" the birds' chance of survival, new research published on Wednesday shows.

Avian pox is a viral disease that has been present in British garden birds such as dunnocks, house sparrows, starlings and wood pigeons since the 1950s. However it was unknown among species in the tit family before 2006, when sightings of infected birds were first reported by members of the public in south-east England.

While all tit species are affected by the new form of the disease, great tits (Parus major) are "by far the most susceptible", shows one of three new papers by the Zoological Society of London (ZSL), the University of Oxford, the British Trust for Ornithology (BTO) and the RSPB, published in the journal PLOS ONE.

Affected birds develop warty, tumour-like growths and lesions, mainly on the head and neck and at the base of the wings. Infection is thought to be spread by biting insects, direct bird-to-bird contact or indirect contact from contaminated surfaces.

Although the disease has a relatively mild affect on some species, it causes severe and large growths on great tits that can prevent them from seeing, feeding or moving around, thereby increasing their risk of predation, starvation and other infections.

Increasing incidents of pox reported by the public between 2006-10 showed the disease spreading further west and north, and in 2011 it reached south-west England, Wales and as far north as Merseyside and the Humber.

Postmortems confirmed that 90% of the outbreaks people had reported in their gardens had affected great tits, and 75% of these cases had involved multiple birds, according to the report.

Genetic studies on the virus showed the sequence matched a strain found in the same species with the same disease in Scandinavia in the 1970s, and more recently in a cluster in central Europe.

"Piecing together the evidence, our most likely hypothesis is that the introduction of the new strain of the virus came either from Scandinavia or Austria, Slovakia, the Czech Republic or Hungary," said Becki Lawson, the lead author on the first paper, ZSL wildlife vet and research fellow and co-ordinator of a national garden bird health initiative run by the BTO and RSPB. "BTO data shows that great tits rarely migrate outside the country, so a more likely explanation is that an infected insect carried the virus across the English Channel on air currents."

Two further papers, also published on Wednesday by the same organisations, took a more local perspective and received emergency funding from the Natural Environment Research Council to intensively study the emergence of the disease as it reached wild tit populations in Wytham Woods, Oxfordshire, in 2009. Using figures from more than 8,000 captured individuals at the site, the team of scientists and vets found the pox in up to 10% of great tits, but in less than 1% of five other closely related species.

Avian pox causes severe and large growths on great tits that can prevent them from seeing, feeding or moving around. Photograph: Jenny Davis/Zoological Society/PA

"Although recovery from infection can occur, our results show that this new strain of avian poxvirus significantly reduces the survival of wild great tits and has particularly large effects on the survival of juvenile birds," said Shelly Lachish of the Edward Grey Institute at Oxford University.

The pox significantly reduces the reproductive output of great tits by reducing the ability of parents to fledge their young successfully and rear them to independence, the research found. Reports also suggested that diseased parents can transmit the pathogen to their offspring, with high mortality rates for affected chicks.

Lachish said that based on the numbers of affected great tits observed at 385 hectares of Wytham Woods, scientific models did not predict that this new disease would cause an overall population decline of the species. "However, pox-affected populations have lower yearly growth rates. Hence, they are likely to have greater difficulty in recovering from other environmental factors that might reduce their numbers," she said.

Since the great tit is a common species across Britain, a continued northward spread of the disease could be expected in the coming years.

Lawson said the team of scientists would continue to work together to monitor the impacts of the new avian poxvirus strain on the population of great tits in the UK. "The next stage is looking in much greater depths at the genetics to try to determine whether the severity of the lesions relates to the virus or the host."

Andre Farrar of the RSPB, said: "Measuring and monitoring is a vital part of understanding any new disease and we'll continue to do that so we can track the spread and intensity of it over time.

"Putting out food in our gardens can be a lifeline for birds during the colder months so it's not necessary to stop feeding, but practising good hygiene at garden feeders is always advisable and any sightings of diseased birds should be reported to the RSPB."

Avian pox is found only in birds, and does not pose a threat to the health of humans or other mammals.

• Members of the public can report sightings of affected birds by emailing wildlife@rspb.org.uk or calling the RSPB on 01767 693 690