In each of the past two years, the number of confirmed and probable cases of Lyme disease reported to Massachusetts’ public health agency has dropped significantly.

But experts say that doesn’t mean that Lyme disease has become any less prevalent or that your odds of contracting the tick-borne illness have gone down.

Instead, officials say, the declines in reported cases in both 2015 and 2016 could be linked to changes in weather patterns. The state faced a drought both years.

“Ticks die unless they are kept moist,’’ said Omar Cabrera, a spokesman for state Department of Public Health. Not only can hot and dry weather reduce tick populations, but those conditions may also mean that more people stay indoors than usual, reducing chances for exposure.

Health officials say that it is very difficult to predict how bad a particular tick season will be. Odds are that we’ll eventually have a season where conditions are favorable for infectious ticks, and Lyme cases will rise again. So health officials say it’s best to be on guard every year.

While Lyme cases declined the past two years, reports of other illnesses spread by the same kind of tick (deer ticks, also known as black-legged ticks) increased in one or both years.

Confirmed and probable cases of anaplasmosis increased from 624 in 2014 to 771 in 2015 and 842 last year. Babesiosis cases dropped from 537 in 2014 to 448 in 2015, but rebounded in 2016 to 518.

Still, Lyme disease is far more prevalent in Massachusetts. State data show there were 5,801 confirmed and probable Lyme cases in 2014, which marked the fourth straight year of increases and the highest total ever recorded.

In 2015, Lyme cases dropped to 4,342 and fell to 3,407 last year, which was the lowest total since 2006.

Thomas N. Mather, director of the University of Rhode Island’s Center for Vector-Borne Disease and its TickEncounter Resource Center, wondered whether the drop in Lyme cases was the result of underreporting. But state officials downplayed that possibility.

Instead, they said, it is possible for the different types of illness to go in opposite directions in some years because tick-borne illnesses like anaplasmosis and babesiosis “are not as widely distributed geographically in Massachusetts’’ as Lyme disease.

“Just as Lyme disease started as a problem on the Cape and Islands and then spread across Massachusetts through the movement of ticks on deer and birds (as well as other animals), similar patterns are being observed with anaplasmosis and babesiosis,’’ Cabrera said. “These diseases are still increasing as their geographic distribution continues to expand in Massachusetts.’’

Matt Rocheleau can be reached at matthew.rocheleau@globe.com. Follow him on Twitter @mrochele