More than 600,000 Americans contracted Lyme and other diseases from infected ticks and mosquitoes between 2004 and 2016, more than tripling the number of reported cases of vector-borne diseases. But the number of actual cases during the 12-year period is in the millions, according to the Centers for Disease Control and Prevention.

In the CDC’s June 1 report of its 2018 Vital Signs, the number of reported disease cases from infected mosquitoes, ticks and fleas climbed from 27,388 in 2004 to 96,075 in 2016 for a total number of reported cases nationwide of more than 640,000. But the CDC estimates that the actual number of cases of Lyme — the most prevalent vector-borne disease — is 300,000 a year, which includes cases that overburdened health care providers don’t report to health departments.

Dianna L. Carboni-Piquette, a Leominster native and former Shrewsbury resident, was one of the 50,234 reported cases of Lyme disease in Massachusetts during 2004-2016. In the CDC report, the Bay State retained its fourth-place ranking of the highest number of reported cases of the disease, behind Pennsylvania (73,610), New York (69,313) and New Jersey (51,578). Connecticut — where cases of arthritis in children were detected in the early 1970s in the town the disease is named for — ranked fifth with 36,727 cases.

Ms. Carboni-Piquette died in 2017 at 39 after a four-year battle with Lyme disease. Michael Piquette said his wife’s death certificate lists the primary cause of death as sepsis and Lyme as the secondary cause.

By all accounts, the couple with advanced degrees were on track to fulfill their plans of retiring early and doing nonprofit work or consulting, and traveling, until Ms. Carboni-Piquette, a senior technical writer for Oracle in Burlington, became too sick to work.

“We don’t know when she was bitten. Some of the nymphs are so small that you’d never see them or notice that you had been bitten. We know she started having some strange symptoms in 2011,” Mr. Piquette said

The couple, who met while she was a freshman at Assumption College in Worcester and he a sophomore at Worcester Polytechnic Institute, traveled a lot on the East Coast and in Northern California, where there is also a lot of Lyme. They enjoyed spending time together hiking, mountain biking and downhill and cross-country skiing.

Ms. Carboni-Piquette suffered with flulike symptoms for four years and was on a combination of antibiotics for more than two years. She would occasionally see minor improvements, but she was forced to go on disability in 2014.

After she became sick, she went through the routine of so many Lyme victims: visiting numerous doctors, many of whom her husband said gave countless suggestions for her fatigue, significant weight loss and other symptoms. An initial Lyme test was negative. But a subsequent Western blot test from popular Igenex Laboratory in California came back positive.

The couple lived in Shrewsbury after they were married in 2001 until 2016 when they moved to Nevada where Ms. Carboni-Piquette's brother, Nicholas Carboni, lives to seek alternative treatments and to avoid New England’s brutal winters. She died the following year.

Mr. Piquette, who was an assistant vice president at MetLife in Boston, still lives in the Nevada area, where he is now semiretired and working on starting a business. He and his late wife’s sister, Marina Carboni of Framingham, are committed to becoming more active in the Lyme community.

Ms. Carboni has been encouraging people to share their stories about Lyme via the federal Health and Human Services Tick-borne Disease Working Group. She spoke at the group’s June 2018 meeting and told the story of her sister’s battle with the devastating disease.

The working group was established by Congress in 2016 for six years as part of the 21st Century Cures Act. According to the website, the purpose is to provide subject matter expertise and to review federal efforts related to all tick-borne diseases, to help ensure interagency coordination and minimize overlap and to examine research priorities. The group submits a report every two years and will present its findings and recommendations to the Secretary of Health and Human Services and Congress. Ms. Carboni said it is her hope that the effort will steer more research dollars to the disease.

Mr. Piquette likens Lyme disease to the AIDS epidemic of the early 1980s. He said a lot of doctors and others downplay the severity of Lyme. And some doctors, he said, will not provide adequate treatment. The Infectious Disease Society of America warns that long-term treatment for chronic Lyme disease with antibiotics is ineffective and could be harmful. Whereas the International Lyme and Associated Disease Society recommends treatment determined by clinical judgment. In some cases, that means long-term treatment with antibiotics.

“I think there needs to be a lot of government money spent on research. This is a devastating illness to many people. Entire families are getting it,” he said. “There needs to be better and more effective antibiotics or other treatment that really focus on Lyme. There currently is no medication out there that’s specifically for Lyme and there needs to be.”

The country is not fully prepared to control the threats of the accelerating trend of tick-borne diseases that has been steadily escalating over the past 25 years, according to the recent CDC report. Local and state health departments and vector control organizations face increasing demands to respond to ticks and tick-borne diseases. Proven and publicly accepted methods are needed to better prevent tick bites and to control ticks and tick-borne diseases. More than 80% of vector control organizations report needing improvement in one or more of five core competencies, such as testing for pesticide resistance. The CDC outlines some recommendations for state and local health departments, universities and other entities to follow to help address the major nationwide health crisis that some have called an epidemic.

The CDC says a number of factors may contribute to the increase in ticks and their geographic spread. “For example, the spread of Lyme disease over the past several decades has been linked to changes in land use patterns, including reforestation in the northeastern United States. Suburban development in these areas has increased the spread of these germs because people, ticks, deer and tick hosts such as mice and chipmunks are in close contact,” the agency explains on its website. Rainfall, temperature and humidity and host populations can also contribute to tick density each year.

Though the CDC's 2018 Vital Signs report does not include data beyond 2016, Dr. Lyle R. Petersen, director of CDC’s Vector-Borne Diseases Division in the National Center for Emerging & Zoonotic Infectious Diseases, said state and local health departments received a record number of cases of tick-borne diseases to the agency in 2017. Reported cases of Lyme disease, anaplasmosis/ehrlichiosis, spotted fever rickettsiosis (including Rocky Mountain spotted fever), babesiosis, tularemia, and Powassan virus all increased from 48,610 cases in 2016 to 59,349 cases in 2017.

“These 2017 data capture only a fraction of the number of people with tick-borne diseases. Underreporting of all tick-borne diseases is common, so the number of people actually infected is much higher,” Dr. Petersen said via email.

Dr. Catherine Brown, epidemiologist with the Massachusetts Department of Public Health, said because there is so much Lyme disease, it’s a huge burden for health care providers to report all cases. When a person is diagnosed through a laboratory test, that information is automatically sent to DPH. But many people are diagnosed without having a laboratory test, she said, leaving it to the provider to report the data.

The reporting problem led DPH in 2016 to shift from using the standard case definition for Lyme disease to an estimation method based on the lab results it receives.

“It’s very burdensome. And in Massachusetts, we know we have a lot of Lyme disease … too much of it. It’s not clear to me if knowing if it's 10,000 or 20,000 or 50,000 cases is helpful in any way,” Dr. Brown said.

“The important thing to do is sharing prevention methods. We know the doctors are doing that and that’s what we’re focusing on as well … helping people understand what they need to do to protect themselves.”

She said DPH is also focusing more on newer tick- and mosquito-borne diseases. Since 2004, nine new germs spread by ticks and mosquitoes have been discovered or introduced.

According to the CDC report, Massachusetts had 1,209 reported cases of mosquito-borne diseases between 2004 to 2016. Puerto Rico had 80,534 reported cases during that period. There were numerous cases and some deaths from flea-borne plague, but none in Massachusetts.

The state has not had any reported cases of mosquito-borne Eastern equine encephalitis since one case in 2013. But, that could change this year, Timothy D. Deschamps Sr., executive director of the Central Massachusetts Mosquito Project, said. The number of cases of West Nile virus is also increasing.

He said the Northboro-based agency, which serves 42 Central Massachusetts communities, started testing for infected mosquitoes two weeks ago. None have been found, but last year, he pointed out, was a busy year for West Nile virus. The number of reported cases of the disease climbed from six in 2005 to 49 last year, according to the DPH.

The relative drought periods during 2004 to the end of 2016 significantly suppressed the species of mosquitoes that circulate EEE among the bird population. In 2017, after the drought conditions ended, there was indication that the mosquito species had recovered, he said.

"We do have some concerns of emergence of EEE in birds because those species have returned to near-normal levels. We will continue to trap and test those species and get an indication of what the risk is for the public from this point forward."

Like Dr. Brown, Mr. Deschamps recommended focusing on taking preventative measures to stay safe.