The increase in the number of MERS cases around the world isn't yet enough to make it a major public health emergency, a panel of World Health Organization experts says.

The panel members met for five hours by teleconference on Tuesday, Dr. Keiji Fukuda, assistant director general for health security with WHO, told a news conference Wednesday.

"What they reached was a consensus that the situation had increased in seriousness and urgency, but does not at this point constitute a public health emergency of international concern," he said.

Worldwide, the virus that causes Middle East respiratory syndrome has resulted in 571 laboratory-confimed cases that have been reported to the WHO, Fukuda said. There have been at least 145 deaths since September 2012, according to WHO. It was in late March that the 200-cases mark was crossed.

Fukuda said there were concerns about whether the ability of the virus to move from person to person could be growing. So far, however, there is "no evidence yet of an increase in the transmissibility of this virus."

The WHO emergency committee noted that hospital outbreaks have been a key factor in the spread of the virus. Asked why infection control is still a problem in hospitals after so many years of effort, Fukuda said that the necessary practices are well-known, but "the most difficult thing … has been about how to get them implemented."

Health officials in Canada are preparing for possible cases.

"There's no ongoing sustained human to human transmission. But we're on guard and we're vigilant and we're well-prepared in Canada," Dr. Gregory Taylor, the country's deputy chief public health officer, said in an interview.

Even handwashing, Fukuda said, is done "pretty inconsistently, and it doesn’t matter what country you’re in."

Infectious disease specialists say that proper infection control early on for suspected MERS patients is key.

For example, a 44-year-old Saudi citizen may have exposed the MERS virus to 20 health-care workers who treated him in Florida, including a doctor who had travelled to Canada.

"The person was examined by a physician today and the swabs were done today and we had the results back already and they are negative," Taylor said of the physician who is in isolation in Canada. The location has not been disclosed to protect privacy.

The doctor came to Canada on holiday, reports no symptoms and had minimal exposure to the Orlando MERS patient, Taylor said.

"We are now in communication with the U.S. CDC because this person would like to go home." When that happens, the Public Health Agency of Canada advises that the individual should wear a mask as a precaution.

Also on Wednesday, a Florida hospital spokeswoman said two U.S. employees who fell ill after contact with the 44-year-old patient have tested negative for MERS.

The exposure happened before health-care officials adopted isolation precautions like wearing a mask, said Dr. Antonio Crespo of Dr. P. Phillips Hospital in Orlando.

The WHO committee took into account recent increase in cases in communities and in hospitals, transmission patterns, and the main observations of a WHO mission to Saudi Arabia between April 28 and May 5. Affected countries gave information, including the measures they have taken to halt the virus.

Elsewhere today, a spokesman for the National Institute for Public Health in the Netherlands said a man returning to that country from Saudi Arabia has been admitted to hospital with MERS — the first known Dutch person to be affected.

The spread of the virus from its base in the Arabian Peninsula has the attention of Canadian experts.

"The general public really in Canada I don't think needs to be terribly alarmed about this issue," Dr. Kamran Khan, an infectious disease physician and scientist at Toronto's St. Michael Hospital, said of the WHO's decision.

"This is really something where people in medical and public health community right now need to be on heightened alert and awareness of this, because there is a very good chance that this virus will wind up in Canada in the not too distant future."

Travel advisories

"The big concern is that this could actually become a much bigger deal in multiple other countries, kind of akin to what SARS did," Dr. Michael Gardam, director of infection prevention and control at the University Health Network in Toronto, told CBC News on Tuesday.

MERS seemed to have caught people in Saudi Arabia unaware before a systematic plan was put in place, he said.

Symptoms of MERS include cough, fever and sometimes fatal pneumonia. There can also be gastrointestinal symptoms. It is caused by the MERS coronavirus, a cousin of the SARS or severe acute respiratory syndrome coronavirus that killed around 800 people worldwide after first appearing in China in 2002. Coronaviruses are also a cause of the common cold.

In Canada and the U.S., the advice to the general public remains that the threat is low and standard precautions for a respiratory virus apply, such as frequent handwashing, avoiding someone who is coughing and sneezing, and staying home when sick.

According to the U.S. Centers for Disease Control and Prevention, the origin of MERS is uncertain, but the virus likely came from an animal source. As well as in humans, the virus has been found in camels in Qatar, Egypt and Saudi Arabia, and a bat in Saudi Arabia. The CDC stresses, however, that it's uncertain if camels are the source of MERS.

The case fatality rate for MERS is about 27 per cent, something doctors need to be careful about, public health experts say. Fortunately, the virus isn’t efficient at spreading person to person.

For health-care workers, masks, eye protection, gown and gloves are recommended when treating patients with respiratory infections.