You've got a blistery rash. It might be chickenpox. Please don't do this.

The health department is monitoring a slight increase of chickenpox in Whatcom County and telling people who have symptoms to call first before heading to the doctor's office or emergency room.

Varicella, the virus that causes chickenpox and shingles, is highly contagious.

Calling ahead allows health care providers to keep other patients in waiting rooms from being exposed, the Whatcom County Health Department said.

The step will help keep chickenpox from spreading and will protect other patients — including pregnant women and people with weakened immune systems —who can become seriously ill if they contract the disease.

The virus is spread through sneezing, coughing or direct contact with chickenpox blisters.

It causes a blister-like rash, itching, tiredness and fever. Symptoms appear about two to three weeks after being in contact with someone who has been infected.

People who think they might have chickenpox should stay home from work or school and avoid people who haven’t been vaccinated, the health department said.

The disease can be severe.

People who haven't gotten the chickenpox vaccine should do so, the health department said.

Kie Relyea: 360-715-2234, @kierelyea