Infectious Diseases

Antiretroviral Therapy for HIV-Infected Adults
Antiretroviral therapy is recommended for all HIV-infected individuals regardless of CD4 count to decrease morbidity and mortality associated with HIV infection.
Goals of antiretroviral treatment are suppression of viral load for maximum possible duration, restore & preserve immunologic function, reduce HIV-related morbidity & mortality and prevent HIV transmission.
Urgent initiation of antiretroviral treatment is recommended in the following individuals: pregnant women, patients w/ HIV with coinfections (HBV, HCV, active tuberculosis), AIDS-defining illness, HIV-associated nephropathy, low CD4 counts, acute opportunistic infections and HIV HBV with evidence of chronic liver disease.
Aspergillosis
Aspergillosis encompasses a variety of clinical syndromes depending on host immunity factors.
It is caused by Aspergillus, an ubiquitous, soil-dwelling, filamentous fungus that grows on soil, food, dead leaves, household dust, etc. It grows best at 37ºC and the small spores are easily inhaled and deposited deep in the lungs.
The most common pathogens are Aspergillus fumigatus, A. flavus, A. niger and A. terreus.
Aspergilloma is a conglomeration of intertwined Aspergillus hyphae, fibrin, mucus and cellular debris within a pulmonary cavity or an ectatic bronchus.
Bronchitis - Chronic in Acute Exacerbation

Chronic bronchitis is an infection of the trachea and bronchi for at least 3 consecutive months for more than 2 consecutive years.
The patient experiences symptoms of increase in dyspnea, sputum volume and sputum purulence over baseline on most days.

Diagnosis is basically based on clinical presentation.

Bronchitis - Uncomplicated Acute
Uncomplicated acute bronchitis is a self-limiting infection of the trachea and bronchi that usually lasts for 1 to 3 weeks. A healthy patient experiences sudden onset of cough, with or without sputum production.
An inflammatory response to infections of the bronchial epithelium of the large airways of the lungs that begins with mucosal injury, epithelial cell damage and release of proinflammatory mediators.
Transient airflow obstruction and bronchial hyperresponsiveness.
Purulence can result from either bacterial or viral infection.
Candidiasis
Candida sp are the most common cause of fungal infections.
 It can cause infections that range from benign mucocutaneous illnesses to invasive process that may affect any organ.
 It is considered as normal flora in the gastrointestinal & genitourinary tracts, but when there is an imbalance in the ecological niche they can invade & cause disease.
Most common risk factors include: broad-spectrum antibiotics use, central venous catheters use, receipt of parenteral nutrition, receipt of renal placement therapy by patients in ICUs, neutropenia, implantable prosthetic devices use & receipt of immunosuppressive agents.
Cellulitis/Erysipelas
Cellulitis is a spreading bacterial skin infection that infects deeply involving the subcutaneous tissues.
It typically occurs in areas where the skin integrity has been compromised.
It may also result from blood-borne spread of infection to the skin and subcutaneous tissues.
It is commonly caused by beta-hemolytic streptococci and Staphylococcus aureus.
Erysipelas is a type of cellulitis with margins that are sharply demarcated, involves the epidermis and superficial lymphatics.
Onset of symptoms is acute whereas cellulitis has an indolent course.
It is more commonly caused by beta-hemolytic streptococci.
Chlamydia - Uncomplicated Anogenital Infection

Chlamydia is a gram negative obligate intracellular bacteria that causes sexually-transmitted infection.

Chlamydia trachomatis is the primary cause of pelvic inflammatory disease (PID) in women which may lead to ectopic pregnancy, infertility, or chronic pelvic pain.
Most infected females are asymptomatic.
But some females may experience vaginal discharge, dysuria, lower abdominal pain, abnormal vaginal bleeding (postcoital or intermenstrual) or breakthrough bleeding, dyspareunia, conjunctivitis, proctitis and reactive arthritis.

Dengue

Dengue infection is caused by the dengue virus that belongs to the family Flaviviridae. It is generally self-limiting and rarely fatal.
There are 4 serotypes (DEN-1, DEN-2, DEN-3, DEN-4). Infection w/ dengue serotype confers lifetime protective immunity to that specific serotype; cross-protection for other serotypes is only short-term.
It is transmitted to humans through the bites of infected Aedes mosquitoes. It is primarily transmitted by female Aedes aegypti, a tropical and subtropical species.Humans & monkeys are the amplifying hosts after the mosquito bite.
After 4-10 days of incubation period, illness begins immediately.
The acute phase of illness lasts for 3-7 days, but the convalescent phase may be prolonged for a week and may be associated with weakness and depression especially in adults.

Diarrhea in Adults - Infectious
Diarrhea is a change in normal bowel movements characterized by increased frequency, water content or volume of stools.
Infectious diarrhea is diarrhea of infectious origin (bacteria, virus, protozoal) and is usually associated with symptoms of nausea and vomiting and abdominal cramps.
Dysentery (invasive diarrhea) has the presence of visible blood in diarrheic stool.
Febrile Neutropenia
Febrile neutropenia is having a fever of ≥38.3 ºC or ≥38 ºC over an hour and neutropenia that is having an absolute neutrophil count (ANC) of <500 neutrophils/mm3 or an ANC <1000 neutrophils/mm3 expected to decline to ≤500 neutrophils/mm3 over the next 48 hours.
The risk of febrile neutropenia is directly proportional to the duration and severity of neutropenia.
Fever is frequently the only indication of infection in the neutropenic patient.
Genital Herpes
Genital herpes is a recurrent lifelong disease with no cure, caused by herpes simplex virus (HSV).
HSV-2 is usually the cause but HSV-1 may occur in up to 1/3 of new cases.
HSV-1 tends to cause fewer recurrences & milder disease than HSV-2.
The incubation period is 2 days-2 weeks after exposure.
Gonorrhea - Uncomplicated Anogenital Infection
Gonorrhea is a sexually or vertically transmitted infection secondary to gram-negative diplococcus Neisseria gonorrhoeae.
It is one of the most common bacterial sexually transmitted infections that may cause pelvic inflammatory disease leading to infertility or ectopic pregnancy.
Most of the infected females are asymptomatic but may present with increased or altered vaginal discharge, dysuria, urethral discharge, abnormal vaginal bleeding, vulval itching or burning, dyspareunia, conjunctivitis and proctitis.
Helicobacter pylori Infection
Helicobacter pylori is a spiral-shaped gram-negative bacterium involved in the development of gastritis, duodenal and gastric ulcers, and gastric cancer.
Infection is strongly associated with the development of gastric epithelial and lymphoid malignancies.
Acute infection is mostly asymptomatic and is acquired through human-to-human contact via gastro-oral and fecal-oral routes.
Adaptability in gastric conditions and production of urease allow it to colonize the stomach.
Hepatitis - Viral
The majority of acute viral hepatitis infections are asymptomatic or they can cause an anicteric illness that may not be diagnosed as hepatitis.
Hepatitis A generally causes minor illness in childhood with >80% of infections being asymptomatic but more likely to produce clinical symptoms in adults. 
Hepatitis B, C, & D may also be asymptomatic.
Hepatitis A is predominantly transmitted through oral-fecal route.
Hepatitis B is transmitted through perinatal, percutaneous, or sexual routes or close person-to-person contact via open cuts and sores.
Hepatitis C infections are transmitted through perinatal, percutaneous, or sexual routes, blood transfusions, or organ transplants.
Hepatitis D's route of transmission is sexual or percutaneous, especially IV drug use.
Hepatitis E is transmitted primarily through contaminated drinking water and oral-fecal transmission.
Herpes Simplex Virus Infection
Primary herpes simplex virus (HSV) infection is first infection with either herpes simplex virus-1 (HSV-1) or herpes simplex virus-2 (HSV-2) in individuals who do not have antibodies to either HSV-1 or HSV-2.
First episode-non primary infection is infection with either HSV-1 or HSV-2 in individuals who have previously existing antibodies against HSV-1 or HSV-2 respectively.
Recurrent HSV infection results from reactivation of latent virus. It is usually brought about by triggering factors eg UV light, immunosuppression.
Orolabial HSV disease is mostly caused by HSV-1 that occurs most commonly in children <5 years of age. It is transmitted through close contact with individuals who have active viral shedding.
Genital HSV disease is caused by HSV-2 that is the usual cause of herpes genitalis. It typically occurs in adults and transmitted through sexual contact.
Impetigo & Ecthyma
Impetigo is a very contagious, superficial, bacterial skin infection that easily spreads among people in close contact.
Most cases occur in children and resolve spontaneously without scarring in approximately 14 days.
Ecthyma is a deeply ulcerated form of impetigo that extends to the dermis.
It has "punched-out" ulcers with yellow crust and elevated violaceous margins.
Most cases occur in children and elderly.
It may be a de novo infection or superinfection.
Infectious Arthritis
The classical presentation of infectious arthritis is acute onset of pain, warmth and swelling of a single joint.
The range of motion is usually decreased.
The knee is the most commonly affected but any joint may be involved.
Fever and chills may be present.
More than 1 joint may be involved in patients with pre-existing joint disease, other inflammatory conditions or severe sepsis, and in some patients infected with certain pathogens eg N gonorrheae, N meningitidis and Salmonella spp.
Infectious arthritis must always be a part of the differential diagnosis in a patient with an acute monoarthritis. 
Infective Endocarditis
Infective endocarditis is microbial infection of the endovascular structures of the heart.
It often presents in an occult fashion and early diagnosis depends on a high index of clinical suspicion especially in patients with congenital heart disease, prosthetic valves or previous infective endocarditis.
The established diagnosis of infective endocarditis is demonstrated by a positive blood culture and involvement of the endocardium detected during sepsis or systemic infection. It may also be established if there is involvement of the endocardium detected during sepsis or systemic infection but blood culture is negative.
Influenza
The clinical spectrum of influenza ranges from asymptomatic infection to primary viral pneumonia that may progress to death.
Patients presenting with influenza-like illness (ie temperature of 37.8ºC, cough and/or sore throat and absence of a known cause other than influenza) might be infected with different types of influenza virus [eg avian influenza (H5N1)] as well as other respiratory pathogens.
A high index of suspicion is needed to recognize influenza in hospitalized patients.
Pneumonia is the most common complication of influenza virus.
Intra-Abdominal Infections
Intra-abdominal infections (IAI) occur due to disruption of the normal anatomic barrier.
In the hollow viscera is where common disruptions occur, which allows intraluminal bacteria to invade and proliferate in the usually sterile area (ie peritoneal cavity or retroperitoneum).
Community-acquired intra-abdominal infection is usually secondary to gastroduodenal perforation, ascending cholangitis, cholecystitis, appendicitis, colon diverticulitis with or without perforation, or pancreatitis.
Uncomplicated IAI infectious process involves only a single organ and does not extend to the peritoneum.
Complicated IAI is when infection extends beyond the hollow viscus of origin into the peritoneal space and may be associated with peritonitis or abscess formation.
Liver Abscess
Liver abscess may result from peritonitis and bowel leakage via portal circulation, direct spread from biliary disease or from hematogenous seeding.
Classical presentation includes fever, jaundice, and right upper quadrant symptoms (pain, guarding, rocking and rebound tenderness).
Biliary tract disease is the most common cause of bacterial liver abscess.
Most pyogenic liver abscesses are polymicrobial (eg enteric facultative and anaerobic species).
Meningitis - Acute, Bacterial

Acute meningitis is the infection of the subarachnoid space and cerebrospinal fluid by bacteria that may cause local and systemic inflammatory response.
There is the classic triad of symptoms of fever, neck stiffness and altered level of consciousness.
Other symptoms include chills, myalgia, photophobia, severe headache, focal neurologic symptoms, nausea, vomiting, seizures and some patients may present with rash.

 

Molluscum Contagiosum
Molluscum contagiosum is an infection due to poxvirus that results into discrete skin lesions with central umbilication.
Spread is by skin-to-skin contact, fomites spread and autoinoculation.
Patients with atopic dermatitis, HIV or immunodeficiency are particularly susceptible.
Incubation period may be from 2-7 weeks.
In children, it usually presents with lesions on the face, scalp, ears, trunk and extremities and crural folds while in adults, it is typically sexually transmitted and affects the groin, genital area, thighs and lower abdomen.
Nontuberculous Mycobacterial Disease
Nontuberculous mycobacteria are ubiquitous and are usually found in soil, natural and treated water sources. They are relatively uncommon cause of pulmonary disease and likely to cause disseminated disease.
May cause both asymptomatic infection and symptomatic disease in humans.
There is no evidence of animal-to-human or human-to-human transmission in immunocompetent hosts.
Nontuberculous mycobacterial pulmonary disease is a generally slowly progressive infection.
Signs and symptoms are generally nonspecific.
Osteomyelitis
Osteomyelitis is an acute or chronic inflammation of the bone due to an infection resulting from hematogenous spread, contiguous spread from soft tissues and joints to bone, or direct inoculation into bone from surgery or trauma.
The infection is generally due to a single microorganism but polymicrobial infections may also occur.
Staphylococcus aureus is a major cause of infection.
Signs and symptoms include fever; inflammatory findings of erythema, warmth, pain and swelling over the involved area; draining sinus tracts over affected bone; limited movement of affected extremity; pain in the chest, back, abdomen or leg, and tenderness over involved vertebrae in patients with vertebral osteomyelitis; anorexia, vomiting and malaise.
Otitis Media - Acute
Otitis media is a general term used to describe inflammation of the middle ear which may be caused by an acute infection.
The symptoms are usually nonspecific and include otalgia (pulling of ear in an infant), irritability, otorrhea with or without fever.
Symptoms of upper respiratory tract infection may also be present.
Parasitic Infections
Gastrointestinal parasitic infection symptoms include abdominal pain, diarrhea, dysentery, flatulence, malabsorption and symptoms of biliary obstruction.
It can be caused by protozoan parasites and helminths.
Host susceptibility factors in gastrointestinal parasitic infections are nutritional status, intercurrent disease, pregnancy, immunosuppressive drugs and presence of a malignancy.
Knowledge of the geographic distribution of parasites is helpful in the diagnosis of patients.
Pityriasis (Tinea) Versicolor
Pityriasis (Tinea) versicolor is a fungal infection caused by Malassezia furfur. It is benign, superficial, and localized to the stratum corneum.
It may present as chronic or recurrent infection and may occur in healthy individuals.
It is more common in summer than winter months.
It presents with multiple well-demarcated macules or patches and finely scaled plaques with hypopigmentation or hyperpigmentation, hence the term "versicolor".
Lesions are usually found on the upper trunk, chest, back and shoulders, and may extend toward the neck, face and arms.
Pneumonia - Community-Acquired
Community-Acquired Pneumonia (CAP) is an acute infection of the pulmonary parenchyma accompanied by symptoms of acute illness and abnormal chest findings.
It is a lower respiratory tract infection acquired in the community within 24 hours to <2 weeks or occurring ≤48 hours of hospital admission in patients who do not meet the criteria for healthcare-associated pneumonia.
It occurs at the highest rates in the very young and the very old.
Potentially life-threatening especially in older adults and those with comorbid disease.
Pneumonia - Hospital-Acquired
Hospital-acquired pneumonia (HAP) is defined as pneumonia occurring ≥48 hours after admission and excluding any infection that is incubating at the time of admission.
Ventilator-associated pneumonia (VAP) is described as pneumonia occurring >48-72 hours after endotracheal intubation and within 48 hours after removal of endotracheal tube.
Early-onset HAP or VAP is the pneumonia occurring within the first 4 days of hospitalization that may be cause by antibiotic-sensitive bacteria that usually carries a better diagnosis.
Late-onset HAP or VAP is the pneumonia occurring after ≥5 days. It is likely caused by multidrug-resistant pathogens associated with increased mortality and morbidity.
Rhinosinusitis - Acute, Bacterial
Acute bacterial rhinosinusitis is the mucosal inflammation of the nose and paransal sinuses caused by bacteria lasting >10 days for up to 4 weeks or symptoms worsening for 5-7 days within 10 days.
It is often preceded by a viral upper respiratory tract infection.
Signs and symptoms are nonspecific and typically difficult to differentiate from viral upper respiratory tract infection.
There is fever with nasal obstruction/congestion or anterior and/or posterior purulent drainage, with or without facial pressure/pain/fullness and reduction/loss of smell.
Streptococcus pneumoniae and unencapsulated strains of Haemophilus influenzae cause half of acute rhinosinusitis cases.
Rosacea
Rosacea is a chronic cutaneous disease of the convexities of the central face (cheeks, chin, nose and central forehead) w/ periorbital and perioral skin sparing. This condition is attributed to chronic vasodilation.
Remissions and exacerbations are common.
It typically appears after 30 years of age but may occur at any age.  It commonly affects fair-skinned individuals.
The common presenting symptoms are facial flushing, stinging/burning erythema, telangiectasia, edema, papules, pustules, ocular lesions, and hypertrophy of the sebaceous glands of the nose with fibrosis.
A history of episodic flushing often heralds onset of rosacea.
Scabies
Scabies is a contagious disease caused by the mite Sarcoptes scabiei var hominis.
The affected individual usually complains of having a highly pruritic rash that occurs at night.
It occurs more often in children <15 years of age, sexually active young adults, the immunocompromised and in persons living in crowded living conditions (eg nursing homes, military barracks).
Transmission is typically by direct skin contact with an infected person and in adults, sexual transmission is common.
Syphilis - Primary
Syphilis is a sexually or vertically transmitted infection caused by Treponema pallidum subspecies pallidum.
A person with primary syphilis has a 60% risk of infecting her sex partner and 70-100% risk of passing the infection to the fetus.
In the primary stage of acquired syphilis, there is an appearance of a painless ulcer (chancre). Then in the secondary stage, there are skin rashes and sores on mucous membranes.
In the latent stage, it is asymptomatic and not communicable. It is in the tertiary or late stage that it is symptomatic but not communicable; it usually appears 10-20 years after 1st infection.
Tinea Capitis
Tinea capitis  is a contagious dermatophytosis affecting the hair shaft and follicles of the scalp, eyebrows and eyelashes.
It is most common in the crowded areas as infection originates from contact with a pet or an infected person and asymptomatic carriage persists indefinitely.
It primarily affects children 3-7 years of age.
The causative agents are the genus Trichophyton and Microsporum.
Cardinal clinical feature is the combination of inflammation with hair breakage and loss.
Tinea Corporis, Cruris & Pedis
Dermatophytoses are superficial fungal infections that have different presentations and are named based on location.
Tinea corporis (ringworm) usually presents with lesions of varying sizes, degree of inflammation and depth of involvement found on the trunk, extremities or face excluding the beard area in men.
Tinea cruris (jock itch) are lesions found on the groin. It may affect the proximal medial thighs and extend to the buttocks and abdomen. The scrotum and penis tend to be unaffected.
The red scaling lesions with raised borders have pustules and vesicles at the active edge of infected area.
Tinea pedis (athlete's foot) are lesions found in the interdigital spaces (most common), sole of foot, and sides of feet.
Tinea Unguium
Onychomycosis is a fungal infection of the nail bed, nail plate or both. It is caused by dermatophytes, non-dermatophyte molds and yeast.
Tinea unguium or dermatophytic onychomycosis is a dermatophyte infection of the nail more commonly affecting the toenails than the fingernails.
It is usually asymptomatic and patients first consult for cosmetic reasons.
It is suspected if there are changes in the 3rd or 5th toenail, involvement of the 1st and 5th toenails on the same foot and unilateral nail changes.
Tonsillopharyngitis - Acute
Patients with group A beta-hemolytic streptococcal pharyngitis have classic symptoms of tonsillar swelling/exudates, tender anterior cervical lymphadenopathy, with no cough but with fever of >38ºC.
Clinical features suggestive of a viral etiology are conjunctivitis, absence of fever, coryza, cough, diarrhea, anterior stomatitis, hoarseness, discrete ulcerative lesions, rhinorrhea and viral exanthem and/or enanthem.
Antibiotics will not be needed for every patient that presents with sore throat but it should not be withheld if the clinical condition is severe or group A beta-hemolytic streptococca is suspected.
Tuberculosis - Pulmonary
Tuberculosis (TB) suspect is any one who has signs or symptoms suggestive of TB (eg >2 weeks productive cough).
Definite TB is considered in patients with culture or molecular line probe assay positive for Mycobacterium tuberculosis, or in patients with at least 1 sputum smear positive for acid-fast bacilli.
TB cases are also classified based on the disease anatomical site, bacteriological results (including drug resistance), previous treatment history and patient's HIV status.
Pulmonary TB is a case of TB that involves the lung parenchyma.
Miliary TB is considered as PTB since lung lesions are also seen.
TB in the pleural effusion, mediastinal and/or hilar lymph nodes with no evidence of abnormalities in the chest x-ray are considered extrapulmonary TB.
Patients presenting with both PTB and extrapulmonary TB are classified as a case of PTB.
Urinary Tract Infection - Complicated
Urinary tract infection (UTI) is complicated if the UTI is associated with factors that increases colonization and decreases therapy efficacy. Factors may include one or all of the following: Structural or functional abnormalities of the genitourinary tract; presence of an underlying disease that interferes with host defense mechanisms or the patient being immunocompromised; and being infected by a multi-drug resistant bacteria.
Principles of therapy includes effective antimicrobial antimicrobial therapy, optimal management of the underlying abnormalities or other diseases & adequate life-supporting measures.
Urinary Tract Infection - Uncomplicated
Acute uncomplicated urinary tract infection (UTI) is one of the most common bacterial infections in adults that may involve the lower or upper urinary tract or both.
Acute cystitis is an infection limited to the lower urinary tract while acute pyelonephritis is an infection that involves the upper urinary tract (renal parenchyma & pelvicaliceal system) that usually has significant bacteriuria.
Recurrent UTI is characterized by 2 episodes of uncomplicated UTI in the last 6 months or ≥3 episodes with positive cultures in the last 12 months in patients with no structural or functional abnormalities.
Vaginitis: Trichomoniasis, Candidiasis, Bacterial Vaginosis

Trichomoniasis is caused by a flagellated protozoan, Trichomonas vaginalis. It is always sexually transmitted.

Bacterial vaginosis is the most common cause of vaginitis, vaginal discharge or malodor. It results from overgrowth of anaerobic bacteria.

Vulvovaginal candidiasis is caused by overgrowth of yeasts where 70-90% of cases are secondary to Candida albicans. It most commonly occurs when the vagina is exposed to estrogen (ie, reproductive years, pregnancy) and may be precipitated by antibiotic use.

Varicella-Zoster Virus Infection
Varicella, also known as chickenpox, is a self-limited benign disease caused by primary varicella-zoster virus (VZV) infection characterized by fever, malaise, and generalized pruritic vesicular rash.
The average incubation period is 14-16 days. It is transmitted via direct contact with vesicular fluid or inhalation of aerosolized respiratory secretions or via droplet route during face-to-face contact.
Hallmark sign is pruritic rash that begins in the scalp and face which eventually spreads to the trunks and extremities.
Warts - Anogenital
Anogenital warts (condylomas) are caused by human papillomavirus (HPV) with >90% of the lesions caused by genotypes 6 & 11.
Patients who present with visible warts may also be infected with high-risk HPVs (eg types 16 & 18) which can cause subclinical lesions that are associated with intraepithelial neoplasia, cervical cancer and anogenital cancer.
Many HPV infections are subclinical, transient, and clear spontaneously within 12 months but may also remain latent and reactivate after several years.
Warts - Cutaneous
Cutaneous warts, also called verrucae, are benign proliferations of skin caused by human papillomavirus (HPV).
Most common warts on the hands and feet are due to HPV types 1, 2, 4, 27 & 57.
HPV is usually transmitted by contact with skin of an infected individual or by transmission of virus living in warm moist environment.
Autoinoculation may occur from traumatizing lesions by biting or scratching.
Incubation period is unknown but may range from months to years.