A vender holds a chicken at a chicken market on in Shanghai, China. At least 17 people have died from a lesser-known strain of bird flu in the country. (AP Photo)

It's time for the world's public health officials to pay very close attention to the new bird flu outbreak in China first detected in March. To put it bluntly, there are now some seriously dangerous developments occurring around the new disease outbreak in China that infectious disease specialists and international public health specialists need to track closely.

Let's start with three new developments reported on earlier this week by Jason Koebler, U.S. News & World Report's science and technology correspondent: the first reported case of the new bird flu strain outside China; the fact that any potential vaccine tests in animals (not humans) may be up to six weeks out; and, more ominously, that Chinese officials suspect that there may be cases of human-to-human transmission in the 100-plus reported cases (which includes 22 deaths).

"The situation remains complex and difficult and evolving. When we look at influenza viruses, this is an unusually dangerous virus for humans," Keiji Fukuda, the World Health Organization's assistant director-general for health security, said Wednesday at a briefing.

Chinese officials – and public health officials around the world – had hoped that this potentially virulent and deadly bird flu strain (H7N9) could be contained inside China and that it would not progress or mutate to the point where humans could transmit the strain to other humans. But, of the patients analyzed so far, half appear to have had no contact whatsoever with poultry

Now, we have the first reported case outside China appearing in Taiwan this week. A 53-year-old male, Taiwanese citizen who worked in the Jiangsu Province in China, developed symptoms three days after returning home, according to Taiwan's Central Epidemic Command Center. And because Chinese officials are also publicly saying at least some of the existing cases may have involved human-to-human transmission, this new bird flu strain could spread – and fast.

None of this is good.

Right now, 18 percent of the cases in China have ended in death. While this is still less deadly than the previous avian flu outbreak in China six years ago – the H5N1 bird flu virus eventually killed more than 300 people after spreading from China to other countries in 2006 – the death rate for this new Chinese bird flu epidemic is more than triple the mortality rate of tuberculosis in China today.

Despite widespread fears among public health officials that the earlier bird flu strain years ago might become a human-to-human pandemic, that didn't occur. Nearly all reported cases of the earlier bird flu strain, while deadly, seemed to jump from poultry to humans who were handling them or in contact with them. For this reason, despite dozens of outbreaks, it was easier to contain the spread.

But if this new bird flu strain does, in fact, become capable of human-to-human transmission, and it takes awhile for a suitable vaccine to be developed, then international public health officials are going to start sweating. And the public, rightly so, will be worried.

One flu virology expert, John Oxford from Queen Mary University in London, told Reuters this week that the emergence of this completely new strain of bird flu infection in humans was "very, very unsettling." This new strain is, in fact, a mixture of three different types of bird flu variants and "seems to have been quietly spreading in chickens without anyone knowing about it," he said. This has likely been going on for at least two years.

Public health officials, in general, have been worried about bird flu viruses for years. Research several years ago showed the virus could be transmitted from an expectant mother to a fetus, and that the virus isn't just contained in the lungs – it can also migrate throughout the body. This new strain is likely to have similar capabilities.

What's more, it could re-ignite fears about the possibility of deadly global pandemics. A decade ago, several well-known virologists and public health experts warned in published papers that the world was at risk for of pandemics that could kill tens of millions of people – or even more – without adequate infectious disease monitoring and medical research. The 2006 Chinese bird flu outbreak came on the heels of those global pandemic warnings.

The good news is that China is more transparent about disease epidemics now than it was a decade ago, and the number of reported cases with the new bird flu strain has not jumped dramatically so far. And China learned a lot about how to limit the spread of bird flu during previous outbreaks, simply by closing down poultry markets that appear to be a likely starting point.

But the fact the new H7N9 strain has now moved outside China – and that Chinese officials are taking a close look at human-to-human transmission possibilities – should send up more than a few red flags. Just because the previous bird flu outbreak in China didn't spread quickly and prove as deadly as some had feared does not mean that this new outbreak will follow a similar course.

If the suspicions of human-to-human transmission potential are confirmed, that alone makes the threat of a pandemic – as opposed to a series of local outbreaks that can be contained with efforts to close down poultry markets or the sale of infected birds – more likely. Chinese media have said in recent days that officials believe some of the cases to be likely human-to-human transmissions. WHO officials have said that this new strain transmits to humans more easily than the previous strain.

In the case of a pandemic, a vaccine would need to be developed and distributed quickly. A California company (Inovio) is in the early stage of developing a potential vaccine, with plans to get access to the virus in a highly protected lab environment for its initial tests. In a worst-case scenario, a vaccine could skip animal tests and be administered to humans.

Let's hope it doesn't come to that –and that public health officials are paying attention.