New Delhi/IBNS: With Covid-19 cases rising again, particularly in six states, the Centre Thursday wrote to the administrations saying they should focus on controlling the sudden spike in the viral infection.

The Union Health Secretary on Wednesday wrote to Maharashtra, Gujarat, Telangana, Tamil Nadu, Kerala, and Karnataka asking them to increase testing, treating, tracking, and vaccination.

"There are few states which are reporting higher number of cases indicating possible localised spread of infection and there is a need to follow a risk assessment-based approach to prevent & contain the infection, without losing the gains made so far in the fight against the pandemic," the letter said.

More than 700 Covid cases were recorded in a single day after a gap of over four months, taking the active caseload to 4,623, according to Union Health Ministry data updated on Thursday morning.

The country recorded 734 cases on November 12 last year.

"It is essential that the state must maintain a strict watch and take pre-emptive action if required in any areas of concern to control the emerging spread of infection," the letter said.

The letter advised states to examine the situation of Covid at the micro level (district and sub-districts), and maintain focus on the implementation of necessary measures for prompt and effective management of Covid-19, "duly ensuring effective compliance with various advisories issued by this ministry".

Health Secretary Rajesh Bhushan had on Saturday as well written a letter to states and union territories flagging a gradual rise in Covid test positivity rates in some states.

Calling it a concerning issue, he said it must be promptly addressed.

Active cases now comprise 0.01 per cent of the total infections, while the national Covid recovery rate has been recorded at 98.80 per cent, according to the health ministry website.