The World Health Organization is warning health care workers everywhere to suspect a disease called Middle Eastern Respiratory Syndrome, or MERS, whenever they see a case of unexplained pneumonia.
Monday's warning comes at the end of a six-day WHO investigation in Saudi Arabia, where 40 of the 55 cases of the respiratory disease have occurred. Sixty percent of those people with known infections died.
Recent samples of these bird flu viruses are only one or two genetic mutations away from developing the ability to latch onto receptors lining the respiratory tracts of humans, biologists at the Massachusetts Institute of Technology say.
"Some of them are one amino acid away from achieving the necessary strength or affinity to latch onto human receptors," Ram Sasisekharan of MIT tells Shots. "That's a key step."
Both viruses have shown themselves capable of infecting people and causing serious illness and death. H5N1 has sickened 630 people over the past decade and killed 60 percent of them.
The H7N9 virus, which popped up this spring in southeastern China, has infected 132 people, 37 fatally, according to the latest WHO tally. Cases have dwindled in recent weeks, and only 14 remain in the hospital. But health authorities worry the virus could return with cooler autumn weather, especially if precautions are eased at the live bird markets that seem to be the source of most infections.
Dr. Anthony Fauci, director of the National Institute of Allergies and Infectious Diseases, says the MIT reports are "important evidence" of how the flu viruses are evolving. "However, that is not the entire story, at all, of how viruses evolve in a way to have sustained transmission," he says.
Fauci says what makes animal flu viruses highly contagious among people is complex and poorly understand. "In fact," he says, "I'm not even sure what the extent of the complexity is."
Reassuringly, he points out that there's never been a flu pandemic involving the H5 or H7 families of viruses.
When it comes to MERS, Fauci says he's taking it "very seriously."
He acknowledges that it's unheard of to have three emerging disease threats to worry about simultaneously.
"I've been doing emerging infections for a very long period of time," Fauci says. "And we usually have one on the radar screen, and occasionally two. But to have three on the radar screen, at least in my experience, is pretty unique."
For all three of the current viral threats, the numbers of people affected so far don't seem so threatening on a global scale. But officials worry that as human infections continue, any of the viruses could acquire the characteristics necessary to spread readily through the air and efficiently infect cells in human respiratory tracts.
With MERS, they're also concerned that some people could become so-called super-spreaders of infection — people who produce large amounts of virus in respiratory secretions and then pass the virus to dozens of others. This is how SARS, a cousin of MERS, spread rapidly to around 8,000 people in 2003, killing 11 percent of them.
"The primary lesson from SARS is we do need to watch for that sort of thing," Dr. Anthony Mounts of WHO tells Shots. "SARS didn't seem so transmissible among normal circumstances. But then we saw these events in which it spread really crazy fast from person to person."
Health authorities worry that the MERS virus might spread among pilgrims expected to visit holy sites in Saudi Arabia next month during Ramadan, or the millions more expected in October for the annual Hajj to Mecca.
Mounts is also concerned the MERS virus could sneak out of the region in the lungs of guest workers. "Pakistan, India, Indonesia, the Philippines all have large populations in the Middle East, and travel back and forth quite a bit," he says.
MERS has already shown its ability to spread within health care facilities in Saudi Arabia, Jordan and France. And its incubation period is believed to be as long as 12 days — plenty of time for an infected person to carry the virus anywhere in the world before falling ill.
Hence the new WHO warning that health care workers everywhere should think about MERS if they encounter unexplained respiratory illness.
Last week's WHO investigation in Saudi Arabia produced no new information on how people are getting MERS in the first place — from what animal source, or by what route.
The purpose of last week's mission to Saudi Arabia, led by WHO assistant director-general and virus specialist Dr.Keiji Fukuda, was to help sort through the data collected by the Saudis to discern patterns of spread and exposure.
There's been mounting frustration among public health workers over the lack of information about MERS coming from Saudi Arabia. Officials there have tended to release numbers of cases with a bare minimum of detail and little or no epidemiologic analysis.
For example, the Saudis startled everyone last month by announcing 13 new cases that turned out to have occurred in a hospital in Al-Ahsa in the kingdom's eastern province. That brought unhappy reminders of SARS, which spread rampantly in health care institutions.
But there has, so far, been no thorough analysis of how the hospital outbreak unfolded.
Similarly, there are reports of a second hospital outbreak involving five cases in a different Saudi town. But the circumstances and location were unclear last week even to WHO workers monitoring the situation.
WHO officials had expected to hold a press conference on Sunday to announce the results of their latest investigation, but that didn't happen. The press release the agency put out on Monday contained only general statements about the MERS outbreaks in Saudi Arabia and lauded the Saudis for doing "an excellent job in investigating and controlling the outbreaks."
The statement noted that "large gaps" remain in the knowledge of MERS, but cautioned that "it often takes time for scientific investigations to produce results."
MERS first appeared in Saudi Arabia last June, and the coronavirus that causes it was first described last September.