Agartala, July 10 : The highly infectious Delta plus variant of coronavirus has been found for the first time in Tripura after the Delta strain was detected in three northeastern states -- Assam, Manipur and Mizoram, doctors said here on Saturday. Agartala Government Medical College (AGMC) Microbiology department head Tapan Mazumder said that after the samples of Tripura were tested in the National Institute of Biomedical Genomics (NIBMG) at Kalyani in West Bengal, 138 cases of Delta plus, 10 cases of Delta (plain) and three cases of UK variant were found in the northeastern state. Majumder, who was present along with Director of Health and Family Welfare Radha Debbarma and Covid-19 Surveillance Officer Deep Kumar Debbarma said that the Delta plus strain is more transmissible and evades the body's immunity. "It is a cause of concern that the Delta plus variants were found in all the eight districts of Tripura and the Delta (plain) and UK variants found in few districts," he told the media. Majumder, who is also the Professor of AGMC, said that Delta plus strain also can reduce the efficacy of the Covid-19 vaccine. The Delta variant of coronavirus has been found for the first time in Assam and then in Manipur and Mizoram following which the doctors and the authorities have asked the people to be more cautious and follow Covid appropriate behaviour. The Delta variant was observed in Europe in March and it was notified and brought into public domain on June 13. Last month, the scientists in Delhi said the highly transmissible Delta variant of SARS-CoV-2 has mutated further to form the 'Delta plus' or 'AY.1' variant, but there is no immediate cause for concern in India as its incidence in the country is still low. The new Delta plus variant formed due to a mutation in the Delta or B.1.617.2 variant, first identified in India, and one of the drivers of the deadly second wave, they had said. With the rising trend of Covid cases, the Tripura government has extended the curfew for another week and tightened the various restrictions from Saturday. The Centre had recently deputed multi-disciplinary teams to three northeastern states -- Arunachal Pradesh, Tripura, and Manipur -- in view of the increasing number of Covid-19 cases being reported from these states. The central teams, consisting of a clinician and a public health expert, are now visiting the states and monitoring the overall implementation of Covid management measures, including testing, surveillance and containment operations, Covid appropriate behaviours and their enforcement, availability of hospital beds, sufficient logistics, vaccination etc. Tripura Covid-19 Surveillance Officer Deep Kumar Debbarma said that the two-member central team led by R.N. Sinha, Director, All India Institute of Hygiene and Public Health, arrived in the state on Monday and is now visiting various districts of the state. /IANS