The Union health ministry on Saturday flagged surges in Covid-19 infections in multiple districts in six states over the past week, urging local authorities to enhance public health measures to contain the escalation amid the threat of omicron’s spread.

Health secretary Rajesh Bhushan sent independent notes to the heads of the health departments of Kerala, Jammu and Kashmir, Karnataka, Mizoram, Odisha and Tamil Nadu, citing worrying spikes in district-level infection counts during the week ending December 3.

Bhushan reaffirmed the need for the states to intensify their “test-track-treat-vaccinate” strategy and promote Covid-19-appropriate behaviour and precautions by the public. His notes flag the districts with unusual surges and high-test positivity levels.

The health ministry had earlier this week urged all the states to enhance surveillance and bolster their health infrastructure and the resources that might be required if omicron surfaced and spread in India. The variant has so far been detected in samples from two patients in Karnataka and one in Gujarat.

But dozens of more samples are still being sequenced and scientists say that more cases are likely to emerge in the coming days to weeks. Health officials have urged the public to adopt all precautions, including wearing masks and avoiding crowds.

Experts say what impact omicron will have on India’s shrinking epidemic remains unclear, although limited data from South Africa has suggested omicron can increase the risk of re-infections.

India has fully vaccinated about 50 per cent of its adults, but experts say the two waves and the continuing epidemic has likely infected over 80 per cent of the population.

Under these circumstances, experts say, any surge should be investigated to determine whether it is driven by omicron.

Kathua in Jammu and Kashmir, for instance, has registered an eight-fold rise in new cases — 405 cases between November 26 and December 2, compared with 49 cases between November 19 and November 25. In Jammu, new cases have increased 53 per cent, from 223 in the week ending November 25 to 342 in the week ending December 2.

The health ministry has identified Thiruvananthapuram, Ernakulam, Kozhikode, Thrissur and Kottayam as districts of concern in Kerala for their high volume of weekly cases.

Four districts — Thiruvananthapuram, Wayanad, Kozhikode and Kottayam — have test positivity rates above 10 per cent, which experts say signal either large epidemics or low testing levels.

In Mizoram, the weekly infection counts in Siaha district increased threefold to 98 over the past week, compared with 29 during the previous week. In Khawzawl, new case counts rose to 92 over the past week from 32 during the previous week.

In Odisha, Dhenkanal has registered the sharpest spike in new infections — a 666 per cent rise from 9 cases between November 20 and 26 to 69 cases between November 27 and December 3. Kandhamal, Nabarangpur, Angul, Kendhujhar and Balangir too have documented increases between 75 per cent and 250 per cent.

In Karnataka’s Tumkur district, the weekly count of new infections increased 152 per cent from 46 between November 19 and November 25 to 116 between November 26 and December 2. The health ministry note to Karnataka has also listed Dharwad, Bangalore and Mysore as other districts of concern.

In Vellore, the weekly case counts increased to 128 over the past week compared with 93 the previous week.