The Andes strain of hantavirus that recently triggered a deadly outbreak on a luxury cruise ship has no natural hosts within China, and no human infections have ever been reported in the country, the Chinese Center for Disease Control and Prevention said on Friday.

Hantaviruses are a group of rodent-borne viruses that cause an estimated 200,000 human infections globally each year. More than 20 hantavirus species capable of causing disease in humans have been identified, and they are broadly divided into two categories.

One category is linked to hemorrhagic fever with renal syndrome, which is characterized by symptoms such as fever, hemorrhage and kidney damage. The disease, also known in China as epidemic hemorrhagic fever, is caused by strains including?Hantaan virus and Seoul virus. China has reported declining numbers of such cases in recent years.

The other category causes hantavirus pulmonary syndrome, with symptoms including fever, dry cough, nausea, vomiting, abdominal pain and diarrhea. Severe cases may lead to respiratory distress and shock. These strains, including the Andes virus, mainly circulate in Argentina, Bolivia, Brazil and other parts of the Americas, where 200 to 300 cases are reported annually.

The strain linked to the cruise ship outbreak, which has killed at least three people and sickened five others, was identified as the Andes strain associated with hantavirus pulmonary syndrome. The cruise ship departed from Argentina on Apr 1, according to the World Health Organization.

The China CDC said hantaviruses spread primarily through inhalation of aerosols contaminated by the urine, feces or saliva of infected rodents, as well as through the consumption of contaminated food or water, contact through broken skin or mucous membranes, or bites and scratches from infected rodents.

It stressed that hantavirus infections generally do not spread from person to person, and that normal social interaction and ordinary contact in public places will not result in transmission.

"There have been a small number of person-to-person transmission cases reported in relation to hantavirus pulmonary syndrome caused by the Andes virus," it said. "Prolonged cohabitation in enclosed spaces may lead to limited transmission through close contact or inhalation of aerosolized pathogens shed by infected individuals."

The China CDC said reducing human contact with rodents is the most effective way to prevent infection. Recommended measures include keeping homes and workplaces clean, avoiding direct contact with rodents and their excreta, properly storing food and drinking water, and disinfecting areas contaminated by rodent waste.

It also advised people working in agriculture, forestry, sanitation and field exploration to receive vaccination against epidemic hemorrhagic fever.