GENEVA, Switzerland (AFP) — A deadly hantavirus outbreak on a cruise ship has spurred global concern over the potential spread of the virus among and from ship evacuees as they head back to their home countries.

Here are the World Health Organization’s main recommendations to limit the transmission risks and to better protect those exposed to the rare virus, which usually spreads among rodents, and for which there is no vaccine or treatment.

– Quarantine –

All of the nearly 150 people who were onboard the Dutch-flagged MV Hondius when it arrived early Sunday in the Canary Islands for disembarkation have been classified as “high-risk” contacts, according to the WHO’s epidemic and pandemic preparedness and prevention director Maria Van Kerkhove.

The United Nations health agency is recommending that all of them be quarantined and kept in isolation for six weeks.

“For people returning home, our recommendations are active monitoring and follow-up and daily checks for symptoms at home or in a specialised facility for the full incubation period of 42 days, after last potential exposure,” the WHO told AFP on Monday, adding that it considered that the isolation period started “on 10 May”.

“Should any early symptoms or sudden onset of respiratory distress occur, people should immediately inform health authorities and self-isolate until medical evaluation is conducted,” the agency stressed.

Why 42 days? Van Kerkhove said that corresponded to the longest likely incubation period of Andes virus — the only hantavirus strain known to spread between humans — at the heart of the outbreak.

Olivier Le Polain, who heads WHO’s epidemiology and analytics for response division, stressed that people are “in the first few days, in the first few moments of illness”, which is why it is wise not to wait for symptoms to appear before placing a contact in isolation.

– What should countries do? –

The WHO has urged countries to strengthen health coordination, contact tracing and surveillance of suspected cases.

The organisation is working with “all of the countries to receive further information about any of the cases that we’re following up, any of the people that might become suspect cases”, Van Kerkhove said.

Other people who had left the ship before the outbreak was understood, as well as people they come in contact with could also be considered high-risk contacts.

WHO has said that high-risk contacts “may include cabin mates, intimate partners, persons with prolonged close indoor exposure, healthcare workers with unprotected exposure, and individuals handling contaminated materials or body fluids without appropriate personal protective equipment”.

The agency has urged countries to provide “clear and transparent communication to affected individuals and the general public” about the situation.

– Various country approaches –

Each country chooses what health protocols it wants to put in place, with most following WHO’s guidelines.

But in the United States, Jay Bhattacharya, acting director of the Centers for Disease Control and Prevention (CDC), said the 17 returning American passengers would not necessarily be quarantined.

Depending on the estimated risk, passengers can choose to go home “without exposing other people on the way”, he said Sunday.

WHO chief Tedros Adhanom Ghebreyesus, who was on Tenerife to help supervise the evacuations, said that policy “may have risks”.

Several countries, including Germany, Britain, Switzerland and Greece, have opted for a 45-day quarantine.

Australia and France, for their part, have announced minimum observation periods of three and two weeks respectively, which can then be extended.

– In healthcare facilities –

There is, as of now, no licensed treatment for hantavirus, which can have a fatality rate up to 50 per cent.

But the WHO said, “early supportive care and immediate referral to a facility with a complete ICU can improve survival”.

The UN health agency recommends that healthcare facilities systematically apply standard precautions to all patients, including hand hygiene, surface cleaning and waste management.

For the management of suspected or confirmed cases, the WHO recommends implementing additional measures, with particular precautions taken in the case of any procedures likely to generate aerosols.