Infectious diseases

Infectious diseases are those caused by organisms such as bacteria, viruses, fungi, or parasites. As healthcare professionals, we know that many of our patients seek treatment for infectious diseases of all sorts. The next several sections discuss common infectious diseases.

Viral hepatitis

Hepatitis is an inflammation of the liver. Inflammation can damage the liver and cause impaired liver function. There are many causes for hepatitis in general, but this material will specifically cover hepatitis that has a viral cause. Viral hepatitis is an infectious disease that, in most cases, can be prevented. Viral hepatitis can be caused by five main viral strains: A, B, C, D, and E.

Hepatitis A and hepatitis E are both transmitted primarily through fecal-oral contact. Hepatitis B, hepatitis C, and hepatitis D are transmitted as bloodborne pathogens. Vaccines are available for hepatitis A and hepatitis B. No vaccine is available in the United States for hepatitis C or hepatitis E. Hepatitis D can infect only a person who already has hepatitis B, so vaccinating against hepatitis B prevents hepatitis D as well.

Sexually transmitted infections

STIs can be seen in any individual who is sexually active. Signs and symptoms of STIs can be vague, nondescript, or absent altogether, so a person can carry an infection and pass it on without ever feeling ill. That is why anyone who is sexually active should be tested for STIs, especially if they have engaged in any high-risk behavior. The individual infections, how each is transmitted, and how each is treated are covered in the chapter on female reproductive system infections and menopause.

Coronavirus 2019 (COVID-19)

COVID-19 was discovered in December of 2019 in Wuhan, China. It quickly became a pandemic. It is caused by the SARS-CoV-2 virus and most often causes respiratory symptoms similar to a cold, flu, or pneumonia. This virus can also attack other parts of the body, and it has gone through several mutations. These mutations or variants are still SARS-CoV-2 but may act differently. Some are more contagious, more severe, or resistant to the treatments that have been developed.

The common signs and symptoms include the following:

• Fever or chills
• New loss of taste or smell
• Cough
• Sore throat
• Shortness of breath or difficulty breathing
• Congestion or runny nose
• Fatigue
• Nausea or vomiting
• Muscle or body aches
• Diarrhea
• Headache

Most people have mild symptoms, but some people become very ill. Those most at risk are older adults and those with underlying conditions such as the following:

• Cancer
• Overweight or obesity
• Chronic kidney disease
• Pregnancy
• Chronic liver disease
• Sickle cell disease or thalassemia
• Chronic lung disease
• Organ or blood stem cell transplant
• Diabetes (type 1 or type 2)
• Stroke
• Heart conditions
• Substance abuse disorders
• Immunocompromised state
• Tuberculosis

In October of 2020, the Food and Drug Administration (FDA) approved remdesivir (Veklury), an antiviral drug, to treat COVID-19. This medication modestly improved recovery time for patients with COVID-19 that needed hospitalization. Several other drugs are being developed and tested.

Infectious mononucleosis

Infectious mononucleosis is also known as mono or the kissing disease. It is commonly acquired as a child or an adolescent. Most children do not show signs and symptoms, or they are very mild. People who acquire the disease in late childhood, adolescence, or young adulthood usually have signs and symptoms. It is generally a mild, self-limiting viral infection, but it can have serious complications, such as hepatosplenomegaly. Mono is passed from person to person via saliva - that’s why it can be passed by kissing. It can also be passed by sneezing, coughing, or by sharing eating or drinking utensils.

Although other viruses can cause infectious mononucleosis, the Epstein-Barr virus (EBV), a type of herpes virus, is by far the most common. Most adults have antibodies to EBV by the end of their 20s. A person is considered immune and cannot have mono again once antibodies develop. Although the disease is usually mild, some people can develop complications and may become very sick.

Risk factors for acquiring mono include activities that involve contact with someone who has an active infection - for example, kissing, sharing food and drink, and sharing eating utensils or toothbrushes. EBV has an incubation period of 4 to 6 weeks for adolescents and young adults.

Signs and symptoms of infectious mononucleosis may include fatigue, fever, swollen lymph nodes in the neck and armpits, sore throat, swollen tonsils (may obstruct breathing or cause wheezing), headache, skin rash, swollen upper abdomen, and soft-swollen spleen. Signs and symptoms usually subside within 2 to 4 weeks. Fatigue and enlargement of the lymph nodes and spleen may last 4 to 6 weeks.

Complications of mono may include an enlarged spleen and pain in the left upper abdomen (the spleen could rupture if left untreated), hepatitis, jaundice, anemia, and thrombocytopenia. Rarely, complications may include myocarditis, meningitis, encephalitis, and Guillain-Barré syndrome. Severe complications can occur in someone who is immune compromised, such as a person with HIV/AIDS or on immunosuppressive drugs.

Diagnostic procedures include the history and physical exam (to look for swollen lymph nodes, liver, and spleen; fever; and sore throat); blood tests, including a Monospot to detect antibodies to EBV; and a CBC and differential to look for an elevated WBC count and atypical lymphocytes in the blood.

Treatment for mono is supportive care - it is a viral infection. Antibiotics are not necessary and are not useful for viral infections. Lots of rest, fluids (especially water), over-the-counter (OTC) pain- or fever-reducing medications (not aspirin), and a healthy diet are the best treatments for mono. Within 2 to 4 weeks, the virus should run its course, and most people recover completely.

One more important treatment for mono is to limit activities while symptoms remain. Staying away from school or work, getting extra rest, and limiting physical activities and sports are recommended. The provider should give the patient permission to resume a normal schedule.

Treating the complications of infectious mononucleosis may include these measures:

• Sometimes streptococcal throat infections can occur secondary to mono. Antibiotics should be used to treat streptococcal infections.
• If hepatosplenomegaly occurs, the person should seek medical attention. Sometimes corticosteroids are given to reduce the inflammation of the liver and spleen.