CALVERT COUNTY, Md. (WJZ) — There’s a medical mystery in Calvert County. A respiratory illness killed almost an entire family.

Jessica Kartalija has the latest on the investigation.

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Three family members are dead and another is still fighting for her life. Now investigators believe it could be a bizarre strain of the flu.

Calvert County’s hazmat team — on full respirators — entered their home looking for samples of a microbe deadly enough to kill three of four family members.

“We got a large family and everybody is concerned about what’s going on,” said a neighbor.

Ruth Blake, 81, died March 1. Her 58-year-old son and 51-year-old daughter died Tuesday.

The Maryland Department of Health and Mental Hygiene has confirmed two family members died of complications of influenza H3  circulating this season, combined with a bacterial infection.

“I’m just concerned. It’s a really big loss to the family,” said a neighbor.

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Maryland Medical Examiner David Fowler says at least one of the bodies was brought to Baltimore City for an autopsy. Blake’s other daughter is being treated at a Washington-area hospital. The three siblings were caring for Blake when she contracted a pneumonia-like illness.

“I think that this is highly unusual and that’s why this is newsworthy but as far as we can tell at this moment, this has been confined to these four individuals and this has been confined to this family group,” Fowler said.

Health officials have contacted members of Blake’s extended family.

“I don’t know a lot. I’m just trying to find out so I can take precautions for my family,” a neighbor said.

School officials in Calvert County are notifying parents to watch for signs of illness.

“It’s upsetting to think that there’s something out there and we don’t know what it’s all about,” a neighbor said.

Flu season goes through May. If you haven’t gotten a flu shot yet, health officials are urging you to get one.

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Health officials also urge anyone who believes they may have contracted the flu to wash their hands often and keep sick children at home.