State health officials in Maryland and California are monitoring a small number of residents for potential hantavirus infection, according to a brief update issued May 12, 2026. The World Health Organization has stressed that the risk to the general public remains low.

Maryland officials are following two individuals. California officials are monitoring four. Neither state has disclosed the specific circumstances behind the monitoring, such as whether the individuals have symptoms, have been exposed to rodents, or have traveled to regions where hantavirus is more common. The monitoring is a precautionary measure.

What monitoring means

In public health, “monitoring” typically refers to active or passive surveillance of people who may have been exposed to a disease. It can include daily check-ins, symptom logs, or lab testing. The fact that these individuals are being watched—not isolated or treated—suggests that health authorities have identified a potential exposure but do not yet consider them sick or contagious.

Hantavirus is not transmitted from person to person in the United States; the primary route is inhalation of aerosolized virus from rodent urine, droppings, or saliva. The deer mouse is the main carrier in North America. That means even if the monitored individuals develop hantavirus, they pose no direct risk to others in their community.

WHO’s assessment

The WHO statement that “the risk to the public is low” is a standard classification used when a disease event is isolated, under control, and unlikely to spread. For hantavirus, that label is nearly always accurate because human cases are sporadic and rare. The United States typically reports fewer than 20 to 30 cases per year, concentrated in the Southwest and rural areas.

By making the statement, WHO signals that no international travel restrictions, trade measures, or public health alerts are warranted. The agency does not provide details about the Maryland and California cases because, at this stage, there may be nothing more to say.

Background on hantavirus

Hantavirus pulmonary syndrome (HPS) was first identified in the United States during a 1993 outbreak in the Four Corners region. Symptoms begin with fever, fatigue, and muscle aches and can progress rapidly to severe respiratory distress. The disease carries a fatality rate of about 30 percent, which is why any suspected exposure draws immediate attention from health authorities.

There is no specific treatment for hantavirus; care is supportive. Prevention relies on avoiding contact with rodents, sealing homes, and cleaning infested areas with proper protective gear.

Because hantavirus is a notifiable disease in the United States, any suspected or confirmed case must be reported to state health departments, who then coordinate with the CDC. The CDC maintains a national surveillance system but has not issued a separate alert about these monitoring cases.

What comes next

For the six individuals under observation, the outcome depends on whether they develop symptoms within the incubation period, which typically ranges from one to five weeks. If they remain healthy by the end of monitoring, they will be released from surveillance. If symptoms appear, they will receive supportive care and confirmatory testing.

For the public, there is no reason to change behavior or avoid Maryland or California. The monitoring is a sign that the public health system is working as designed: catching potential exposures early, watching closely, and assessing risk. The WHO’s “low risk” classification is consistent with that approach.

SysCall News will follow this story and provide updates if any of the monitored individuals test positive or if health officials release additional details. For now, the situation is contained, and the number of people involved is small.