China reported three more cases of human infection of the H7N9 bird flu virus on Sunday, raising the total number of cases to 21 all in the eastern part of the country.

NPR: WHO Talks With China On Sending Bird Flu Team

But in the current issue of The New England Journal of Medicine, Thai doctors report two cases of apparent human-to human transmission of the bird flu.

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In other domestic news, the World Health Organization is watching out for mutations and possible human-to-human transmission of the new H7N9 bird flu strain after two family cluster cases - a father-and-son cluster and a husband-and-wife cluster - were detected in Shanghai, China Daily reports.

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The country's Ministry of Health had then moved to allay fears over the outbreak, saying that although further human bird flu cases were possible throughout China, there wouldn't be a large-scale outbreak, Xinhua and CCTV said.

CNN: China records its fourth bird flu death this year