A senior health official in Shanghai on Wednesday denied media reports that the city might have delayed reporting the outbreak of the previously lesser-known H7N9 bird flu to the national health authorities.

"We finally confirmed the deadly virus on March 20 and soon sent the virus sample to the national disease control department," Lu Hongzhou, deputy director of the Shanghai Public Health Clinical Center and a leading public health expert in the city, told China Daily.

The Southern Metropolis Daily reported on Wednesday that the Shanghai health department confirmed the H7N9 virus on March 10 but reported the virus to the national health department 12 days later, triggering public speculation that Shanghai had deliberately delayed reporting the case.