A debilitating disease caused by ticks infects up to 200 people a year in Ireland.
The seasonal spike in cases of Lyme's disease, which can lead to chronic fatigue, was revealed by experts who warn campers to be wary as the peak time for bites begins.
"From April onwards is the time when we expect to see Lyme disease most frequently, because this is when ticks are most plentiful," said Dr Paul McKeown of Health Protection Surveillance Centre (HPSC).
He urged people to use common-sense protection such as insect repellent and suitable clothing to keep the infected mites at bay.Ramblers
"Preventing Lyme disease means preventing tick bites," Dr McKeown added.
"Anyone who spends time outdoors should protect themselves against tick bites. This includes ramblers, campers, mountain bikers, people who work or walk in woodland, especially in grassy areas."
Wednesday sees the start of May and Lyme Disease Awareness Month, when the tiny bloodsuckers are most active.
The commonest symptom is a rash, but the bites can cause brain fog and heart disease in the worst instances.
"Cases of a more severe form of Lyme disease - neuroborreliosis - have to be reported to the HPSC by doctors and laboratories in Ireland," Dr McKeown continued.
"There are approximately 10 to 20 cases of neuroborreliosis notified in Ireland each year.
"However, as some people will not be aware they are infected, or will not seek medical help, the true number is not known.
"It is likely that there are at least 100 to 200 cases of the milder forms of Lyme disease in Ireland annually. People can find lots of information and resources on the HPSC website."
Anyone developing itchy skin is advised to visit their GP, who may prescribe antibiotics to nip the disease in the bud.
Safeguards include long trousers and shirts, avoiding going barefoot and checking skin and hair - especially the neck and scalp of children and fur of pets.
The mites are found in both urban and rural settings.