Bird Flu China: Dead pigs, swans and ducks linked to three new fatalities A leading science writer has speculated that the unexplained deaths of thousands of pigs, ducks and swans in China is linked with the recent human bird flu fatalities and heralds the start of a pandemic. Residents in Shanghai began to spot dead pigs floating down Huangpu River on March 10. Days later dead ducks were found in the Nanhe river in the southwestern Chinese province of Sichuan. By the end of the month, the carcasses of at least 20,000 pigs as well as tens of thousands of ducks and swans had been washed up on riverbanks across China. Linked? A leading science writer has suggested the 16,000 dead pigs that washed up in Shanghai could be connected with China's latest bird flu outbreak Meanwhile two Shanghai men aged 87 and 27, were diagnosed with a new strain of the Bird Flu and died. Today, it was announced that a third victim died in hospital in Hangzhou city on March 27, bringing the number of confirmed human infections to nine. All the casualties were infected with the H7N9 form of influenza, a type which had not previously been known to infect human beings. Authorities are still unable to explain the deaths of the animals, although most people have automatically assumed that China's notoriously polluted waterways are responsible. Flashpoint: The first two bird flu victims were infected in the city of Shanghai, where thousands of dead pigs were washed up last month Research: A technician holds test reagents for H7N9 bird flu virus at the Beijing Center for Diseases Control and Prevention Tests on some of the dead pigs later revealed evidence of PCV-2 - a virus that is harmless to human beings, as well as birds. However PCV-2 it is only supposed to be fatal to fetuses and newborn piglets and the pigs tested were all adult. In an intriguing piece, Pulitzer Prize-winning science writer Laurie Garrett has now suggested that the virus that killed the pigs could be linked to the new strain of bird flu. A nurse attends to a patient in Shanghai where an emergency response plan has been activated following the two bird flu deaths Writing for the highly respected foreignpolicy.com website, she said: 'One very plausible explanation for this chain of Chinese events is that the H7N9 virus has undergone a mutation -- perhaps among spring migrating birds around Lake Qinghai. The mutation rendered the virus lethal for domestic ducks and swans. Because many Chinese farmers raise both pigs and ducks, the animals can share water supplies and be in fighting proximity over food -- the spread of flu from ducks to pigs, transforming avian flu into swine flu, has occurred many times. Once influenza adapts to pig cells, it is often possible for the virus to take human-transmissible form. 'That's precisely what happened in 2009 with the H1N1 swine flu, which spread around the world in a massive, but thankfully not terribly virulent, pandemic.' Today Chinese authorities dismissed such speculation and insisted that the H7N9 outbreak was not linked to the animal deaths. Yin Ou, deputy director of the Shanghai Municipal Agricultural Committee, told reporters that the city had tested 34 dead pigs found in the city's Huangpu River for the H7N9 virus, but the tests had all come back negative. Flu experts around the world are currently studying samples isolated from the patients to assess its human pandemic potential. At least 1,000 dead ducks were found floating in the Nanhe river in southwestern China Of the seven other cases of the new strain, two have died, both in the business hub of Shanghai. The other five are in a critical condition in hospital in Nanjing. Shanghai, Nanjing and Hangzhou are all close to each other in eastern China. The first birds were infected in 1996, while the disease spread to a humans for the first time in Hong Kong a year later. It began to move throughout Asia before cases were later found in Europe Experts have warned the high contagious disease is the world's biggest pandemic threat and could kill between 5 million and 150 million people. The disease is expected to continue mutating within birds but has largely been brought under control in Asia due to vaccination programmes. Seventeen governments around the world are preparing vaccines to combat a pandemic. The Agriculture Ministry said it had yet to find any animals infected with H7N9, though added it was possible it had been brought to China by migratory birds. The World Health Organization (WHO) says so far it has seen no evidence of human-to-human transmission, but there are questions about the source of the infection and about how it may be being transmitted into people. 'We still don't know the mode of transmission or host (of the virus),' said WHO spokesman Gregory Hartl. Those are the two most important pieces of information we would need. In order to control it, we need to know where it is coming from. China has a chequered record when it comes to tackling disease outbreaks, which some officials have previously sought to cover up. However, since the H7N9 cases have been identified, China has stepped up its alert level and said it is being transparent in dealing with them. In 2003, authorities initially tried to cover up an epidemic of Severe Acute Respiratory Syndrome, which emerged in China and killed about a 10th of the 8,000 people it infected worldwide.