BEIJING (AP) -- China reported Tuesday that four more people in one province have been seriously sickened by a bird flu virus new to humans, as cities along the eastern seaboard stepped up public health measures to guard against the disease, which has already caused two deaths.
The health bureau of eastern Jiangsu province said three women and a retired man from different cities in the province were all critically ill with the H7N9 virus, a diagnosis confirmed by the provincial disease prevention center. The cases are the second batch to be confirmed after three in Anhui province and nearby Shanghai on Sunday.
The H7N9 bird flu virus has previously not been a problem in humans. That compares to the more virulent H5N1 strain, which began ravaging poultry across Asia in 2003 and has since killed 360 people worldwide, mostly after close contact with infected birds.
The reports of the new cases suggest that authorities are taking a closer look at severe flu cases after identifying the first known infections on Sunday.
"When you don't look, you don't find them, but when you look, you'll find," said Dr. Ray Yip, a public health expert who heads the Bill and Melinda Gates Foundation in China.
"A lot of people get severe respiratory conditions, pneumonias, so you usually don't test them. Now all of a sudden you get this new reported strain of flu and so people are going to submit more samples to test, (so) you're more likely to see more cases," Yip said.
All of the new patients have been sick since about March 19, when they had fevers, coughs and other flu-like symptoms, the Jiangsu health bureau said in a statement. Their conditions worsened over periods of time ranging from a week to 11 days and they were transferred to intensive care units in the provincial capital, Nanjing.
Based on the statement, only one of the patients appeared to have had daily contact with birds — a 45-year-old woman who was described as a poultry butcher. The four cases did not appear to be connected, and other people who have had close contact with the patients have not reported having fevers or respiratory problems, it said.
The provincial health bureau said it was strengthening measures to monitor suspicious cases and urged the public to stay calm, joining Beijing and China's financial capital, Shanghai, in rolling out new steps to respond to the virus.
The three earlier cases reported Sunday included two men who died in Shanghai, resulting in the city activating an emergency plan that calls for heightened monitoring of suspicious flu cases. Under the plan, schools, hospitals and retirement facilities are to be on alert for fevers, and administrators are to report to health authorities if there are more than five cases of flu in a week.
Cases of severe pneumonia with unclear causes are to be reported daily by hospitals to health bureaus, up from the weekly norm. The plan also calls for stronger monitoring of people who work at poultry farms or are exposed to birds.
"The health bureau will take effective and powerful measures to prevent and control the disease, to make sure the flu epidemic is effectively guarded against and to safeguard the health of the city's residents," said Xu Jianguang, head of the Shanghai Health Bureau.
Health officials said this week there was no evidence that any of the three earlier cases, who were infected over the past two months, had contracted the disease from each other, and no sign of infections in the 88 people who had closest contact with them.
Health authorities in Beijing also upped the capital's state of readiness, ordering hospitals to monitor for cases of flu and pneumonia without clear causes, the official Xinhua News Agency reported.
The announcements, which lacked many details, show that the government has become mildly more transparent in handling health crises than it was a decade ago during the SARS pneumonia epidemic. Then, as rumors circulated for weeks of an outbreak of an unidentified disease in southern Guangdong province, government silence contributed to the spread of the virus to many parts of China and to two dozen other countries.
Scientists are closely monitoring these viruses for fear they could mutate into a strain that easily spreads among people, but there's no evidence of that occurring.
Associated Press researcher Fu Ting in Shanghai contributed to this report.