A tropical parasite transmitted through rats and snails has caught the attention of health officials in Hawaii. But few scientists have studied the infection once it makes its way into humans, and researchers can’t say for certain whether the disease is becoming more widespread.

The parasite, Angiostrongylus cantonensis, typically resides in a rat’s pulmonary arteries and is commonly known as “rat lungworm.” When its eggs hatch, tiny larvae are shed in the animals’ feces and eaten by snails or slugs. Those slugs, in turn, are often mistakenly eaten by people, on unwashed produce or in drinks that have been left uncovered.

Although the larvae can’t grow into adult worms in a human host, they still can cause various complications, including flulike symptoms, headaches, stiff necks and bursts of nerve pain that seem to shift from one part of the body to another. M.R.I. scans suggest that the worms can also wriggle into the brain, leading to eosinophilic meningitis, which in rare cases can cause paralysis.

Doctors in the state have noted cases of rat lungworm disease since at least 1959. But it is difficult to diagnose. To better track it, and to identify areas that prevention efforts should target, the Hawaii Department of Health began monitoring rat lungworm infections about a decade ago. From 2007 to 2017, officials tallied 82 cases, two of which resulted in death. Another 10 cases were reported in 2018, and six more have been reported among visitors and residents already this year.