Infectious Diseases

Bacteria are among the Earth’s earliest forms of life. They are small infectious agents. Bacteria are divided into thousands of different species but are broadly classified by their shape:

• Rod-shaped bacteria are termed bacilli.
• Ball-shaped bacteria are called cocci.
• Spiral-shaped bacteria are known as spirochetes.

Bacterial cells are further grouped by whether they form clusters, chains or other groupings when viewed through a microscope.

Bacteria live on or in almost every surface, material and environment. A bacterium’s ability to absorb nutrients and tolerate specific environmental conditions makes it more, or less, likely to infect humans.

Treating Bacterial Infections

There are many antibiotics, or medicines, to treat bacterial infections. Antibiotics prevent bacteria from performing key functions to survive. In addition, highly effective vaccines have been developed to prevent bacterial infections.

Research is underway to develop vaccines to prevent the most common causes of hospital-acquired infections, which are often resistant to common antibiotics.

Decades ago, Lyme disease was a mysterious childhood illness in rural Connecticut. Now it’s the most common tick-borne illness in the United States.

Lyme disease is caused by Borrelia burgdorferi, which is carried by the deer tick, Ixodes scapularis. Deer and mice commonly bring infected ticks into contact with humans. Beginning in springtime, tiny deer tick nymphs can attach to a human host. If they remain attached for 24 to 36 hours, they can feed on the human host’s blood and — if the tick is infected — transmit Lyme disease.

Lyme disease usually appears several days to two weeks after a tick bite. A large, red rash may accompany fever, muscle and joint aches, headache and fatigue. Sometimes the rash will appear with multiple rings that may move around on the skin. If the infection is left untreated, it may resolve on its own or get worse.

The most common long-term problem from Lyme disease is arthritis in the joints. Less commonly, neurological infection can occur. This may cause meningitis (with headache, fever and stiff neck) or a facial droop (Bell’s palsy). Infection of the heart is fairly rare, but can cause a brief blockage of electrical conduction in the heart muscle. Each of these conditions is helped with antibiotic treatment. Death from Lyme disease is extremely rare.

Testing for Lyme Disease

When considering Lyme disease, doctors will assess three major issues:

• The likelihood you were exposed to a Lyme-infected tick
• Whether you have a typical illness
• Results of blood tests 

Although most cases of Lyme disease produce clear blood test results, testing too early in the course of illness (for example, when a rash first appears) won’t detect infection about half the time.

Treating Lyme Disease

Typically, Lyme disease is easily treated with an oral antibiotic. Sometimes, more severe forms of Lyme disease require a course of intravenous (IV) antibiotics.

Preventing Lyme Disease and Tick-Borne Diseases

To prevent Lyme disease and other tick-borne infections:

• Wear long sleeves and tuck in pants when you’re in the woods or near other tick-infested areas.
• Carefully inspect and remove ticks as soon as possible.
• Use insect repellents containing DEET.

Other Tick-Borne Infections in the Northeast

Although less common than Lyme disease, these and other tick-borne infections are found in the Northeastern U.S.:

• Babesia microti is a protozoan that parasitizes red blood cells, causing anemia. This generally is a mild disease. But bites from deer ticks infested with both Lyme disease and Babesiosis can cause more severe symptoms. In addition, patients who have had a their spleen removed could have more severe (occasionally fatal) illness.
• Ehrlichiosis occurs in two predominant forms; human granulocytic Anaplasmosis (HGA) and human monocytic Ehrlichiosis (HME). HME is rare in the Northeast, where HGA is most common. Similar to Babesiosis, HGA can cause co-infection with Lyme disease and more severe symptoms. HGA alone can cause significant fever, aches and, occasionally, death. Prompt treatment with an antibiotic called doxycycline is highly effective.
• Tularemia is caused by Francisella tularensis. Symptoms range from skin ulcers and swollen lymph nodes to severe pneumonia and a frequently fatal illness similar to typhoid fever. Tularemia is most often caused by contact with rabbits. Infection can occur by direct contact, through tick bite or by inhaling the bacteria.
• Rocky Mountain spotted fever (RMSF) is caused by Rickettsia rickettsii, a species of bacteria that is spread to humans by dog ticks. Initial signs and symptoms include sudden onset of fever, headache and muscle pain, followed by a rash. The disease can be hard to diagnose in the early stages. Without prompt and appropriate treatment, it can be fatal.

There are more than a million species of fungi, but only about 400 cause diseases in humans, animals or plants. There are two broad groups of fungi: yeasts and molds.

Viruses are small infectious agents of genetic material (either DNA or RNA) contained in a protective protein covering called a capsid. Viruses cannot survive on their own. They must use a host to survive.

Virus particles use proteins to attach to host cells. Once inside host cells, viruses take over and multiply. Viruses may:

• Lie dormant for long periods of time.
• Establish a persistent long-term infection without damaging the host cell.
• Kill host cells when releasing copies of itself.

Viruses affect humans by direct transmission from person-to-person through:

• Contact with airborne droplets from a sneeze or cough.
• Contaminated blood.
• Hand-to-eye or hand-to-mouth contact.
• Mouth-to-mouth contact.
• Sexual contact.
• Less often, an insect, such as with yellow fever or West Nile virus.

Examples of common viral diseases include the common cold, HIV, influenza, chickenpox (varicella virus), hepatitis viruses, infectious mononucleosis (Epstein Barr virus), mumps and measles. In addition, some viral agents (such as smallpox) can be aerosolized and become bioterrorism agents.

Treating Viruses

Antibiotics used to treat bacteria are not effective for treating viruses. A number of antiviral agents have been developed to specifically treat certain viruses, most notably HIV, herpes viruses, and hepatitis B and C viruses.

The main way we treat viral infections is prevention through immunization. Vaccines are available to prevent several significant human diseases, including poliomyelitis, measles, mumps, rubella, tetanus, hepatitis B, influenza, rabies and smallpox. Vaccines are made from a greatly diminished or killed virus.

Sexually transmitted diseases (STDs), or infections, affect millions of people each year in the United States. But most people don’t know the risks and consequences of most STDs.

Most prevalent among teenagers and young adults, many STIs don’t show symptoms, especially in women. Due to the lack of noticeable symptoms, STIs often aren’t diagnosed.

Even without symptoms, STIs are infectious to sex partners. That makes regular screening is important for everyone who’s had more than one sexual partner.

What can you do to limit the spread of STIs?

Not having sex is the only sure way to avoid STIs. Here are other safety tips:

• Use barrier protection such as condoms.
• Limit your exposure to STIs. Unprotected sexual activity increases your chance of exposure and infection. If you or your partner has more than one sexual partner, this increases your chances of getting an STI.
• Look at your partner for any noticeable signs of infection before having sex. If you see any rashes, sores, discharge or swelling, stop and talk about the importance of getting an STI test before having sex.
• If you think you may be infected with an STI, avoid any sexual contact. Visit your primary care physician, a local STD/STI clinic or a hospital. If possible, bring your sex partner(s) with you so that they can be treated, if necessary.

Types of STIs

Generally, your primary care doctor will request a consultation with an ID specialist since these illnesses need to be managed carefully. For your health and safety, follow your doctor’s instructions to make this appointment.

To schedule your own visit at Lahey Clinic, call 781-744-8000.

Appointment Hours

• Monday through Friday: 8:00 am – 5:00 pm

Some insurance plans require a referral from your primary care physician before being seen by an ID specialist. Be sure you get this referral before you see the specialist. Call the number on your insurance ID card to learn about your specific policy.

Information Needed by the ID Specialist

Before your visit, your ID specialist needs all medical records related to your condition. Your physician may forward some of it. Be sure these items are available during your visit:

• Complete list of your medications (especially important is birth control pills, since some antibiotics cause them to be less effective)
• Any known allergies
• X-rays
• Laboratory reports
• A hospital discharge summary (if you were hospitalized)
• Immunization records

Examining germs carefully under the microscope, ID specialists make a diagnosis and coordinate a plan to treat your disease. One of many laboratories at Lahey, the main purpose of our Microbiology Lab is to help diagnose infectious diseases.

ID specialists often order lab tests to examine samples of blood and other body fluids or cultures from wounds. A blood serum analysis can help us detect antibodies that tell the type of infection you have. Often these advanced studies can further explain the results of earlier tests, helping to pinpoint the specific cause.

We review your medical data, including X-rays and lab reports. We also may perform a physical exam to learn what’s causing your symptoms.

Treatments consist of prescription medicines from a pharmacy — usually antibiotics — to help fight the infection and prevent it from returning. Antibiotics may be given to you orally (in the form of pills or liquids) or directly into your veins through an IV.

Many ID specialists have IV antibiotic therapy available in their offices, which lowers the chance you’ll need to stay in the hospital.

Resistance to antibiotics has increased in recent years. Infections that occur in the hospital setting are often caused by bacteria that are resistant to commonly used antibiotics. Some of the most common resistant bacteria are:

• Clostrioides difficile.
• Methicillin-resistant Staphylococcus aureus (MRSA).
• Vancomycin-resistant Enterococcus (VRE).

Using antibiotics when they aren’t needed is a major reason why bacteria develop resistance to them. Antibiotics shouldn’t be prescribed when they can’t help, such as for viral infections.

For this reason, at Lahey, the most powerful antibiotics can be prescribed only by infectious disease experts and other specialists. We also monitor overall use to ensure antibiotics are being used only when needed.

Learn more about our ongoing clinical trials and research specific to antibiotic-resistant bacteria.

Infections can occur after many types of medical procedures, particularly surgery. To avoid getting an infection in the hospital:

• Wash your hands carefully after handling any soiled material, especially after using the bathroom.
• Do not be afraid to remind doctors and nurses about washing and/or disinfecting their hands before working with you.
• If you have an IV catheter or open wound, keep the skin around the dressing clean and dry. Tell your nurse right away if the dressing becomes loose or wet.
• If you have diabetes, discuss with your doctor the best way to control your blood sugar before, during and after your hospital stay. High blood sugar increases your risk of infection.
• If you are overweight, losing weight will reduce the risk of infection after surgery.
• If you smoke, join a smoking cessation program. This will reduce your chance of developing a lung infection while in the hospital and also improve your healing after surgery.
• Carefully follow your doctor’s instructions on breathing treatments and getting out of bed. Ask for help, advice or pain medication when needed.
• Ask your friends and relatives not to visit if they feel sick.
• Ask questions to fully understand your treatment plan and expected results from your care. This will greatly help your recovery.