KUALA LUMPUR, July 15 — The new strains of Covid-19 are highly contagious and can spread through the air in as short as 15 seconds, Health director-general Tan Sri Dr Noor Hisham Abdullah said today.

He said the surge in infections since June 26 is largely spread by the Delta variant, and called on the public to take greater precaution.

"If we look at the infectiousness for a normal virus, the R0 or Rt is between 2.5 and 3.0, but the R0 or Rt for the Delta variant or variants that we have identified is much higher, that is between 5.0 and 8.0.

"Meaning, if 100 people are infected, within a short period of incubation, it can infect between 500 and 800 people,” he said in a news conference broadcast on Facebook.

He added that the virus has been evolving rapidly as well.

He said experts previously estimated that the virus could be transmitted to the closest person who is less than one-metre away within 15 minutes.

"We are informed that with these new variants now, infection can happen within 15 seconds only, and also because it’s airborne,” Dr Noor Hisham said.

He reiterated the importance of vaccination, and pointed to Labuan as an example. At one point, it had the highest number of cases per population of 100,000 people, outstripping even Kuala Lumpur, Negri Sembilan and Selangor.

Dr Noor Hisham said that Covid-19 cases in the tiny federal territory soared to 1,340, within a week at one point.

He attributed the spurt to the Delta variant which spread from workers in the shipping industry there.

He said Labuan saw cases declining in under three weeks after the government stepped up vaccination there.

He added that 52 per cent of those in Labuan have completed both doses of the vaccine.

"Today, there are only 26 cases in Labuan,” he said.