Health warning issued as incurable rat disease kills four people in two US states

Officials have issued a health warning over an incurable rat disease after four people died from the infection this year.

Hantavirus — which is fatal in 36 percent of cases — typically causes about 30 cases per year in the US, mostly in western and southwestern areas.

But some states are now recording a surge in the disease.

In infection hotspot Arizona, officials have issued a warning after recording seven cases and three deaths this year — compared to 11 cases in the six years from 2016 to 2022. 

There have also been two cases and one death in California, including in a county that hasn’t detected the virus for two decades.

Recent extreme temperatures coupled with heavy rainfall are thought to be fueling an uptick in infections in some areas, as these lead virus-carrying rodents to seek shelter from heat and rain indoors — where they come into contact with humans.

The heavy rain can also boost plant growth and the food supply for rodents, leading to more rodent activit and, later, a possible surge in their population.

Arizona health officials said: ‘Hantavirus is a severe and sometimes fatal respiratory illness.

‘It is not limited to one geographic location. It can be present in many areas in the southwestern region of the United States where there is rodent activity, even if mice are never seen.’

Rats and mice can carry hantavirus but not suffer any symptoms.

But they can deposit it in their droppings, saliva and urine — with the virus being breathed in by humans if they disturb contaminated surfaces.

Patients initially suffer an abrupt onset of fever, muscle aches, nausea and abdominal pain nine to 33 days after infection.

Hantavirus is carried by rodents such as the deer mouse (pictured). It causes no symptoms in them but can be spread in their urine or saliva

But this then progresses to difficulty breathing in a condition called Hantavirus Pulmonary Virus. 

This is where the virus infects cells lining tiny blood vessels in the lungs, causing them to start to leak and filling the lungs with fluid. Death occurs due to respiratory failure or shock.

There are no specific treatments for the condition, with doctors instead relying on IV drips and over-the-counter medications to ease symptoms.

Colorado and New Mexico are the places where most hantavirus infections occur, with each having recorded 119 cases since 1993.

Arizona has the third highest tally, at 85 cases, followed by California, 78 cases, and Washington, 59 cases. 

In April, a person in Sierra County, California, died from hantavirus — the first case in the area for more than two decades.

Officials said at the time: ‘Although it is rare, hantavirus can be very serious and deadly.

‘About three cases of hantavirus disease are reported each year in California, and about one in three people with hantavirus disease die.’

There are concerns that the disease may be diagnosed in new areas more often, as warming temperatures cause shifts in the locations of rodents.