Joe Tarrant's family had plenty of reasons to worry about him.

Complications during his birth left him developmentally disabled. By the time he was 5, doctors discovered that only one of his kidneys was fully functional. Decades of wear on his healthy kidney ultimately destroyed that organ.

By age 40, he required a kidney transplant.

Still, Joe led a full life, including lots of outdoor activities.

"His kidney was fine. His heart was fine," big brother Patrick Tarrant, who lives in Newtown, recalled recently.

"If he hadn't gotten bit by the mosquito, he'd still be doing well."

Joe contracted West Nile fever in 2014, presumably from the bite of a mosquito carrying the virus. For most people, such a bite would have been a minor annoyance.

But with his immune system suppressed by the antirejection drugs he took to protect his transplanted kidney, Joe couldn't fight off the infection. He died in 2015 at age 55.

"You can see from pictures and everything, we were always outside. Never a passing thought about mosquitoes," said Patrick Tarrant. "I was completely stunned when the doctor said he didn't know the risk of immunosuppression and West Nile."

Now, with summer mosquito season upon us, Tarrant wants to spread the word that for people like his brother, bug bites can be far worse than itchy.

"I'm thinking, if you've had a transplant, that yearly you should get a medical update about the risks of being outside around mosquitoes," he said.

Loren K. Robinson, deputy secretary for health promotion and disease prevention with the Pennsylvania state Department of Health, agrees that transplant patients and their doctors must take extra care, no matter how long ago the transplant occurred.

"It's really important and even if you feel great, to be as diligent at year 15 as on day one," she said.

According to the U.S. Centers for Disease Control and Prevention, most people who come into contact with a mosquito carrying West Nile virus do not even develop symptoms. Only one in five will develop a fever. And about 1 in 150 will develop a serious, sometimes fatal, neurological illness.

The people who are at greatest risk of serious illness are those with some type of compromised immunity. This can be due to age (people over 60 are at greater risk), malnourishment, or having certain medical conditions, such as cancer, hypertension, or kidney disease, as well as organ-transplant patients who are on immunosuppressants. It is interesting that people with HIV don't face an elevated risk of West Nile, as the specific part of their immune system that is affected is different from that of other kinds of suppressed immunity.

It also can be difficult to recognize when the source of illness is a mosquito bite because reaction times vary.

"Incubation periods vary by person," said Robinson, "The red bump [from a mosquito bite] people get is from day one to three. Sickness is from day three to seven. So people might not associate their sickness with the bite. When people get a fever, it's recommended that they hydrate and rest.

"With a more serious condition, when they get West Nile encephalitis or meningitis, they get a headache, stiff neck and high fever [over 101 degrees]. Those are symptoms that people need to be seen in an emergency room for."

Stephen J. Gluckman, an infectious disease physician at Penn Medicine, notes that even for people with immune problems, a fate such as Joe Tarrant's is rare.

"We send a funny message to people," Gluckman said. "We really want them to be careful, but we don't want them to be terrified. Only a handful of people get neurological problems."

West Nile virus was first reported in the United States in 1999. Between then and 2015, 1,884 deaths from the virus have been reported across the country. Nineteen people died in New Jersey between 2000 and 2015, and 32 in Pennsylvania between 2001 and 2015.

Mosquito bite prevention includes using a mosquito repellent that contains DEET (less than 30 percent for adults and less than 10 percent for children). DEET also repels the mosquitoes that carry Eastern equine encephalitis, Zika, chikungunya, and other diseases, though Eastern equine encephalitis is rare in Pennsylvania and the two others are only a risk when travelling. DEET also repels ticks that carry Lyme disease to some degree, Robinson said.

Covering up with long pants, long-sleeved shirts, and shoes and socks, especially when you're outside for a long time, also is wise. And because mosquitoes breed in standing water, it's important to dump outdoor tubs, pots and other receptacles.

Mosquitoes also don't like wind. Windy days are the best days to be outside, according to Robinson.

"Parking yourself in front of a fan is a great repellent," Gluckman said.

215-854-5502@CaseyAGilman