Vectorborne & Zoonotic Diseases



Vectorborne and zoonotic diseases (VBZD) are infectious diseases whose transmission involves animal hosts or vectors. Zoonotic diseases can be transmitted from animals to people or, more specifically, are diseases that normally exist in animals but can infect humans. Vectorborne diseases result from an infection transmitted to humans and other animals by blood-feeding anthropods, such as mosquitoes, ticks, and fleas. Examples of vectorborne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria. Six out of every 10 infectious diseases in people are zoonotic or vectorborne, according to the CDCWhile many vectorborne and zoonotic diseases are rarely seen in the United States (U.S.), they continue to be a public health concern as we are susceptible to vectorborne and zoonotic diseases found in warmer climates due to global trade and travel. 

Vectorborne & Zoonotic Diseases Data Overview

 Check out the points below for the main takeaways from this page. 

• Lyme disease is the most prevalent tick-borne disease in New Hampshire (NH), and NH has one of the highest incidence rates in the country. Hillsborough has fewer cases per 100,000 when compared to the rest of the state, likely due to city lifestyles in Manchester and Nashua. 

• Anaplasmosis cases have increased 58% in NH since 2014. In 2019 there were 311 cases reported for the entire state, compared to 131 cases in 2014. 

• The Nashua Division of Public Health and Community Services Environmental Health team's arboviral surveillance program oversees the collection of mosquitoes that are analyzed for Eastern Equine Encephalitis (EEE), West Nile Virus (WNV), and Jamestown Canyon Virus (JCV). A positive result for all arboviral tests in mosquito batches occurs 0.17% of the time.

Tick-borne Diseases

Lyme Disease

Lyme disease is the most common vectorborne disease in the U.S. Lyme disease is mostly caused by the bacterium Borrelia burgdorferi. It is transmitted to humans through the bite of an infected blacklegged tick. Symptoms often include fever, headache, fatigue, and a skin rash. If untreated, infection can spread to the joints, the heart, and the nervous system. Most cases of Lyme disease can be treated with a few weeks of antibiotics. Lyme disease is preventable through use of insect repellent, prompt removal of ticks, application of pesticides, and minimization of tick habitat. The ticks that transmit Lyme disease can occasionally transmit other tickborne diseases as well.


Anaplasmosis is a disease caused by the bacterium Anaplasma phagocytophilum. These bacteria are spread to people through tick bites primarily from the blacklegged tick and the western blacklegged tick. People with anaplasmosis will often experience fever, headache, chills, and muscle aches. In the U.S., anaplasmosis is most common in the Northeastern and upper Midwestern states. 

Anaplasmosis cases have steadily increased since 2000, the year the disease became reportable. The U.S. saw a peak of cases in 2017 at 5,762, however the case count in 2018 was substantially lower. The number of reported cases of anaplasmosis is highest among males and people over 40 years of age.


Babesiosis is caused by microscopic parasites that infect a person's red blood cells. Many species of Babesia parasites have been found in animals, and several have also been found in people. Babesia microti is the main species found in people in the U.S. Babesia microti is spread by blacklegged ticks or deer ticks. Transmission is most common in parts of the Northeast and upper Midwest, and usually peaks during warmer months. Babesia is preventable and treatable. Infection can range in severity from asymptomatic to life threatening.

For more information about other tick-borne diseases, visit the CDC.

Mosquito-borne Disease

Mosquito-borne diseases are spread through the bite of an infected mosquito. These diseases include Zika virus, West Nile virus, Eastern Equine Encephalitis, Dengue, and Malaria. Although some people may not become sick after an infected mosquito bite, some people will experience mild, short-term illness or more rarely, severe or long-term illness. Severe cases can even cause death. People at risk include outdoor workers, business travelers who may travel to areas with mosquito-borne diseases, laboratory workers who may work with potentially infected samples, cultures, or arthropods, and healthcare workers who may handle patients who are, or might be infected with certain mosquito-borne diseases.

Arboviral Surveillance

The Nashua Division of Public Health and Community Services (DPHCS) Environmental Health Arboviral Surveillance Program oversees the collection of mosquitoes that are analyzed for Eastern Equine Encephalitis (EEE), West Nile Virus (WNV), and Jamestown Canyon Virus (JCV). The graph below and to the right highlights all positive results for EEE, JCV, Powassan Virus, and WNV in human, mosquito, and animal specimens in NH from 2015-2018. The graphs also show the number of specimens tested in comparison to the number of positive results for that same time period. A positive result for all arboviral tests in mosquito batches occurs 0.17% of the time.


Rabies is a fatal but preventable viral disease. 

Rabies can spread to people and pets if they are bitten or scratched by a rabid animal. In the U.S., rabies is mostly found in wild animals like bats, raccoons, skunks, and foxes. In many other countries around the world, most rabies deaths in people are caused by dog bites. The rabies virus infects the central nervous system. If a person does not receive appropriate medical care after exposure, the virus can cause disease in the brain, causing death. Rabies can be prevented by vaccinating pets, staying away from wildlife, and seeking medical care after potential exposures before symptoms start.

Emerging Coronaviruses

Coronaviruses are a large family of viruses that can cause illness ranging from the common cold to more severe respiratory illness. Novel coronaviruses, like SARS, MERS, and COVID-19, are coronaviruses that jumped the animal to human species barrier.

Middle East Respiratory Syndrome (MERS) 

MERS is a viral illness caused by a coronavirus known as Middle East Respiratory Syndrome Coronavirus (MERS-CoV). Many people with MERS developed severe respiratory illness with symptoms such as fever, cough, and shortness of breath. Approximately 3 or 4 out of every 10 patients reported with MERS have died.

Severe Acute Respiratory Syndrome (SARS)

SARS is a viral respiratory illness caused by a coronavirus known as SARS-associated coronavirus (SARS-CoV). The first report of SARS was in February 2003 in Asia. SARS had spread to more than two dozen countries in North America, South America, Europe, and Asia before the 2003 SARS global outbreak was contained. Since 2004, there have been no known cases of SARS reported anywhere in the world.


Several early cases of COVID-19 were associated with the Huanan Seafood Wholesale Market in Wuhan City, China, which indicates that the virus is likely to have a zoonotic origin. For more information on COVID-19, visit our COVID-19 Update page

Check out the links below for other pages related to Vectorborne Diseases 

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