Chapter 32. Infectious Diseases

Confirming an Outbreak

Confirming the existence of an epidemic is not always straightforward. In part, that is because clear definitions of outbreak thresholds do not exist for all diseases. For some diseases, a single case may indicate an outbreak. These include cholera, measles, yellow fever, shigella, and the viral hemorrhagic fevers.

General guidelines for meningococcal meningitis are that for populations >30,000, 15 cases/100,000 persons/week in 1 week indicates an outbreak. However, with a high outbreak risk (i.e., no outbreak for 3+ years and vaccination coverage <80%), this threshold is reduced to 10 cases/100,000 persons/week. In populations <30,000, an incidence of 5 cases in 1 week or a doubling of cases over a 3-week period confirms an outbreak.

For malaria, an increase in the number of cases above what is expected for the time of year among a defined population in a defined area may indicate an outbreak.1

Post-Disaster Infectious Diseases

Following natural disasters, multiple factors increase the risk of contracting a communicable disease. These include inadequate sanitation, crowded conditions, food shortages, contaminated water, and inadequate immunization. Take all preventive measures possible and be alert for signs of potential epidemic diseases to avoid or quell a secondary disaster.

The diseases listed in Table 32-1 are common following disasters. All but tetanus have the potential of developing into epidemics. The best strategy is prevention, since adequate resources may not be available for treatment—or there may be no good treatment. Unfortunately, some preventive measures, such as hand washing, may not be easy to abide by in austere circumstances.

Conserve scarce resources for those who can benefit from them by limiting treatment to those who have a reasonable chance of surviving. The definition for "reasonable" depends on the amount of resources available in relation to the number of patients.

Immunizations

Individuals who are not used to giving intramuscular (IM) injections, including physicians, dentists, pharmacists, and EMTs, may be asked to help during mass immunizations or when trained personnel are scarce or are busy elsewhere. As a reminder, IM injections and immunizations can be given in the lateral arm in the deltoid muscle; in the anterior thigh, especially with infants or struggling psychiatric patients; or in the upper outer-quadrant of either buttock (to avoid hitting the sciatic nerve). Do not give flu shots or rabies vaccine anywhere but in the arm. Administer rabies immune globulin half at the bite site and half in the arm that does not get the vaccine.

Cholera

Acidification of water rapidly kills Vibrio cholerae organisms. Adding the juice of one lime to a liter of drinking water is sufficient, depending on the type of lime, to rapidly kill Vibrio. This technique has been successful in multiple locations around the world where the local limes' pH is <2.5. In any cholera outbreak, it is prudent to first test the local limes' ability (i.e., pH level) to kill Vibrio before suggesting it to the population.4,5

Decontamination

Many diseases may be transmitted through contact with body fluids, including hepatitis B virus, hepatitis C virus, and human immunodeficiency virus (HIV). Use hypochlorite concentrations ranging from 500 (1:100 dilution of household bleach) to 5000 ppm (1:10 dilution of household bleach) to clean spills of blood or body fluids such as cerebrospinal fluid and peritoneal fluid. The concentration depends on the amount of organic material to be cleaned up and the area to be disinfected. During Clostridium difficile outbreaks, disinfecting environmental surfaces with dilute sodium hypochlorite solutions (between 500 and 1600 ppm) effectively reduces the levels of environmental contamination.6

Stability of Hypochlorite (Bleach) Solutions

When 1:100-dilution hypochlorite solutions are stored in non-opaque spray or wash bottles, they retain 40% to 42% of their initial activity 30 days later. Solutions diluted 1:50 or 1:5 that are stored in closed brown opaque bottles retain their original activity at 30 days.

Either store hypochlorite solutions in sealed brown opaque bottles or prepare the initial hypochlorite dilutions at twice the final concentration of the chlorine level desired following 1 month of storage. For example, to have a solution containing 500 ppm of available chlorine on day 30, prepare an initial solution containing 1000 ppm of chlorine.6

Infection Prevention among Health Care Workers

Additional standard precautions (SPs) for use when resources or improvised resources are available can be found in Table 32-2.

Syndromic Treatment

Clinicians use the constellation of patient-reported symptoms and observed physical signs to diagnose and treat patients. They often add imaging and laboratory testing; these may not exist in austere situations. Therefore, clinicians have to go back to the basics, relying on their knowledge and experience. In international medicine, this has been called "syndromic treatment." In the old days, we called it good medical practice. The primary disadvantage of using this approach is the overdiagnosis and overtreatment it promulgates.7

Syndromic treatment regimens must be adapted to the local disease prevalence, antibiotic susceptibility, medication availability, and the patient's ability to follow up.

Exposure and Incubation Periods

A history of specific exposure, and the interval until disease onset, can often suggest the diagnosis, as illustrated in Table 32-3.

Pattern Recognition

Only awareness and reasonable suspicion can help signal the presence of an epidemic, a new disease, or the use of a biowarfare agent in the civilian community. Alerting authorities to any of the following problems may get you assistance; it may also signal the onset of some austere times ahead. Clues are:

• Previously healthy people present with severe diseases, including severe pneumonia, sepsis (possibly with coagulopathy), fevers and rash, and diplopia with progressive weakness.
• Multiple patients with similar complaints present from a common location.
• Many more patients than normal present with fever plus respiratory or gastrointestinal complaints.
• An endemic disease appears during an unusual time of year.
• The occurrence of an unusual number of rapidly fatal cases.

Sexually Transmitted Diseases

Tests for Sexually Transmitted Diseases

Sexually transmitted diseases (STDs) constitute a huge problem. In developing countries, due to technical and cost constraints, the most useful tests to confirm the diagnosis of STDs are the Gram stain (gonorrhea, bacterial vaginosis); wet mount (Trichomonas); and rapid plasma reagin (RPR; syphilis) tests. Even these tests may not be available in many locations, so the syndromic treatment described in the following paragraphs is the best option.

Sexually Transmitted Disease Syndromes

Treating presumed STDs using the following criteria leads to a higher proportion of patients being treated and, in some cases, a lessening of the disease's prevalence in communities. Patients with these syndromes are usually treated at their first visit. If possible, treatment is a single dose of antibiotics taken immediately. Patients must return after 7 days if treatment fails (i.e., symptoms persist or return).8

Vaginal Discharge

Treat for gonorrhea, chlamydia, Trichomonas vaginalis, and bacterial vaginosis whether or not pruritus is present. If it appears to be Candida albicans, treat only for that. Three non-medication treatments often are effective against vaginal yeast infections. The first is to have the patient sit in a pan of clean, warm water containing vinegar or yogurt twice a day until she feels better. Or, have her mix 3 tablespoons of vinegar in 1 L of boiled, cooled water; then soak a piece of cotton in this liquid and insert it into her vagina each night for three nights. Remove the cotton each morning. The third alternative is to insert the cotton as above, but soak it in 1% gentian violet.9

Lower Abdominal Pain (Female)

In a female patient with painful cervical motion that is not a surgical/obstetric emergency, treat for pelvic inflammatory disease (PID): gonorrhea, chlamydia, anaerobic bacteria, T. vaginalis, and bacterial vaginosis.

Urethral Discharge Syndrome (Male)

Discharge is spontaneous or present after "milking" the urethra. First, treat for gonorrhea and chlamydia. If the treatment fails, treat for T. vaginalis or, if antibiotic-resistant gonorrhea is suspected, add second-line therapy.

Genital Ulcer Syndrome

If patients present with genital ulcers (but excluding typical herpes blisters), treat for chancroid and syphilis. In countries with a high prevalence of granuloma inguinale (donovanosis), treat for that. Improvised treatment for typical vaginal herpes lesions is to treat the discomfort, rather than to cure the problem. Other than analgesics (see Chapter 13, Analgesics), locally applied agents can often help. Tell the patient to apply ice directly to the area as soon as it feels like a new outbreak is occurring. The patient can also hold a wet cloth soaked in cooled black tea or clove tea on the lesions. Other options are to apply witch hazel or a paste of baking soda or cornstarch in water to the lesions.10

Epididymo-Ochitis (Male)

The patient has a hot, tender, painful scrotum. If there is no evidence of surgical (trauma, tumor, torsion) or medical (mumps) causes, treat for gonorrhea and chlamydia.

Inguinal Bubo

Patients have painful swollen inguinal lymph nodes without an ulcer. If there is no other infection causing regional lymphadenopathy, treat for chancroid and lymphogranuloma venereum.

Pharyngitis

Group A beta-hemolytic Streptococcus (GABHS) causes only about 10% of adult pharyngitis cases, although it may be higher in children.11 Antibiotic treatment benefits only those patients with GABHS infection. To determine which patients should get antibiotics, use Centor's criteria12: no cough, tender anterior cervical lymphadenopathy, a history of fever, and tonsillar exudates. Each of these equals 1 point. (Remember them as "CAFE" criteria: Cough absent, Adenopathy, Fever, Exudate.) Without the ability to test for streptococcal pharyngitis (including cultures in children), treat only those patients with ≥3 criteria (points).13 Always treat patients who have 4 criteria.

Bacterial Meningitis Mortality

When deciding how to allocate scarce resources, consider that the risk of death among patients with a single episode of community-acquired meningitis is twice as high for patients ≥60 years old as it is for patients <60 years old. The risk of death is three times higher for those with obtunded mental status on admission than for those who are awake, and four times greater for those in whom seizures began within 24 hours of admission.14 This trend can be extrapolated to other causes of meningitis.

Diagnosis and Communicating with Consultants

Describing lesions correctly also helps make the diagnosis, either when using the algorithms found in many texts or when speaking with consultants. Table 32-4 gives the standard nomenclature for skin lesions. Figure 32-1 illustrates some of these lesions.

Once the lesions are described, use a standard algorithm, such as the one in Table 32-5, to narrow the possible diseases.

After a diagnosis is made and the patient is being followed or has been referred for consultation, documenting their condition may be problematic, especially when trying to identify specific lesions. Measure the lesion and then localize it. One way to localize it is to mentally place the center of a clock face over a specific, identifiable point on the patient's anatomy (e.g., right tragus, left nasal ala, right nipple) and then describe the lesion(s) in relation to that point. For example, to document a lesion 2 inches above and behind the left eye (Fig. 32-2), write "0.4-cm lesion 5-cm 1 o'clock left lateral canthus." For a lesion 2 inches behind and below the left side of the nose, write "0.6-mm lesion 5-cm 4 o'clock left ala." This pinpoints the lesion and facilitates a later comparison by you or another clinician. This is especially helpful when there are several lesions in the same area. In addition, this system is easily understood.16

Tinea Versicolor

Tinea versicolor is a common skin condition caused by an overgrowth of yeast on the skin, primarily in oily areas such as the neck, upper chest, and back. It results in an uneven skin color (dyspigmentation) and scaling, and it may be pruritic.

To treat this condition, use an antifungal cream. If one is not available, make a cream with sulfur and lard (1 part sulfur to 10 parts lard) and apply it to the whole body every day until the lesions disappear. Although treatment of the infection takes a few weeks, it takes a few months for the pigmentation to return as the epidermis replaces itself. Even better is to treat the lesions with sodium thiosulfate, which anyone still developing photographic film will have on hand. Dissolve a tablespoon of this in a glass of water and apply it to the whole upper body. Then rub the skin with a piece of cotton dipped in vinegar. The treatment often must be repeated every 2 weeks to keep the spots from returning. Selenium sulfide (in dandruff shampoo) or Whitfield's ointment may also help, but it must be applied in 5 to 10 minutes before getting into the shower. Use it daily from the neck down for 4 to 6 weeks. (Julie Dixon, MD, in a written communication, received September 4, 2008.) Whitfield's ointment is a mixture of 6% salicylic acid and 12% benzoic acid (or 6% benzoic acid plus 3% salicylic acid) in a lanolin or petroleum jelly base. All these ingredients are readily available and inexpensive. Although effective, treatment with Whitfield's ointment can be uncomfortable, since the patient feels a burning sensation.

Herpes Zoster

Herpes zoster is a reactivation of the varicella zoster virus along any dermatome in the body, although it rarely occurs on the extremities. To ease the discomfort of herpes zoster, use a light bandage over the area so that it does not rub on or stick to clothing. Zoster pain and post-herpetic neuralgia often respond to tricyclic antidepressants (e.g., amitriptyline) better than to narcotics. Post-herpetic neuralgia sometimes responds to hypnotherapy. Patients would need to do self-hypnosis, which is not difficult. See "Hypnosis" in Chapter 14, Anesthesia—Local and Regional, for details.

Topical lidocaine under occlusive patches works well both for acute pain and for post-herpetic neuralgia; its action may last up to 1 week. Use it as a cream, gel, ointment, jelly, or solution. In general, place about 700 mg lidocaine under a 10-cm × 14-cm occlusive dressing.

Both the acute attack of zoster and post-herpetic neuralgia have been successfully treated with a topical licorice (Glycyrrhiza glabra, Glycyrrhiza uralensis) gel. While safe topically, it can be dangerous if given orally.17

Verruca (Warts)

Duct tape seems to work on common warts if applied continuously (24 hours at a time; change after bathing) for 6 (out of 7) days of the week. This treatment takes weeks or months to work, but the wart eventually becomes macerated and then stimulates a host immune response and eliminates the virus. (Dr. Julie Dixon, a dermatologist in Tucson, AZ. Personal written communication received September 4, 2008.)

For those using liquid nitrogen to freeze a wart, it helps to have steady hands. An alternative is to funnel the liquid nitrogen spray directly onto the lesion using a plastic earpiece from an otoscope. This removes any fear of damaging the surrounding tissue.18 Another method is to dip a cotton-tipped applicator into the liquid nitrogen and press it into the tip of an otoscope held above the lesion. As you press harder on the applicator, more liquid nitrogen is released.19 These treatments also likely require a number of applications over a few months.

Cutaneous Myiasis

Cutaneous myiasis may be the one parasitic disease amenable to alternative treatments. It is caused by botfly (Dermatobia hominis) maggots under the skin. They have strong hooked spine rings around their midsections, and so cannot be removed easily while alive.

Many folk methods supposedly remove the larvae, including by using venom extractors (which are of no use for extracting venom); by occluding the skin hole with petroleum jelly, beeswax, or pork fat or sealing the hole with duct tape to reduce their air supply; or by applying native tobacco leaf, injecting ether or chloroform, or topically applying 5% chloroform in olive oil to immobilize the larvae. Natives of endemic areas claim that putting a small piece of meat over the affected area will eventually cause the larvae to burrow through the meat to gain access to oxygen, at which point the meat may be removed with the larvae trapped inside.

Two certain methods to remove the larvae exist. The safest and surest method of ridding oneself of botflies is to wait for the fly to develop and leave the body on its own (this takes about a month). That is both uncomfortable and a bit discomfiting. However, there may be no other option. If surgical skill and equipment exist, and the lesion is in an area without vital superficial structures, the botfly can be removed by excising an ellipse of skin and subcutaneous tissue, including the larva's subcutaneous burrow. Leave the wound open to heal by secondary intention. No antibiotics are necessary.20

Cholera

Cholera treatment consists of measuring output and replacing that amount with electrolyte-containing fluids. This treatment is extremely effective in reducing the case-fatality rate (CFR) in outbreaks that can normally reach as high as 50%. The first trick is to measure the massive output.

To determine the volume of "rice water" stool output, place patients on cholera beds, if possible. These are cots with a hole in the middle; buckets to collect the output are placed beneath the hole (Fig. 32-3). Using these beds allows patients, in their weakened state, to stay in their beds (and avoid possible cross-contamination of others) rather than going to a latrine. This practice also simplifies nursing care. In an epidemic, however, such beds may be at a premium. Rather than putting two patients in one bed (a common practice), which makes the bed much less useful and much more uncomfortable, improvise these beds using military stretchers. Cut a circular, 40-cm-diameter hole in the middle to fit the patients' buttocks. (Cut a smaller hole, of course, for children.) Then put the stretcher on blocks with a bucket underneath the hole.21

Once you have determined the output, begin treatment by rehydrating the patient. Oral rehydration therapy (ORT) is amazingly effective. For patients presenting in shock, limited IV therapy precedes ORT. See Chapter 11, Dehydration/Rehydration, for additional information on ORT and on making oral rehydration solutions (ORS).

Malaria

The best treatment for malaria is prevention. However, the disease is endemic in the tropics. Although antimalarial drugs are widely available, increasing resistance makes the choice of medication a moving target. When treating malaria, an alternative to administering quinine intramuscularly or intravenously in children is to administer it intra-rectally. This method has been used successfully in children with severe malaria or with malaria with severe emesis and no diarrhea. The dose of the injectable quinine dihydrochloride administered via intrarectal tube is 20 mg/kg bid diluted in 2 mL water.22

In patients diagnosed with falciparum malaria, hematuria on the urine dipstick is highly sensitive and specific for impending renal failure. This can be used in conjunction with or in the absence of appropriate blood tests. The presence of urine protein does not have the same correlation.23

Convalescent Serum

In situations where no antibiotics or, more likely, no antiviral agents are available or effective, transfuse serum or the blood from a patient that has recovered from the disease. Without adequate treatment for some viral illnesses that have high case-fatality rates, the use of convalescent serum as a treatment may be the only option—if blood-banking facilities are available.

In the early, pre-antibiotic 20th century, convalescent serum taken from patients who had just recovered from the same disease was routinely used to treat patients with scarlet fever, measles, poliomyelitis, erysipelas, mumps, and pneumonia. This serum was obtained at various times (e.g., 4 to 7 weeks after patients had scarlet fever). The results of treatment using convalescent serum depended on the timing of the treatment and the disease. For measles, small aliquots of serum (5 to 10 mL) injected into susceptible contacts of an active case within 6 days of exposure prevented the disease. If the serum was given 6 to 9 days after exposure, it modified the disease. After that, it was of no benefit.24

More recently, convalescent serum has been used to treat hemorrhagic fevers in animals and humans with good results.25 For the human cases, the serum was obtained from patients discharged from the hospital after recovering from Ebola virus 4 to 6 weeks earlier. Their blood was typed, tested, and anticoagulated per standard blood bank protocols. Adults received an infusion of between 250 and 400 mL of blood. Children received 150 mL infusions. While only 1 of 8 patients receiving convalescent serum died (much lower than the normal CFR), it is unclear what role the serum played in this.26

This "old medical trick" has also been successfully applied to treat "severe cases of H1N1 flu." In those cases, clinicians gave plasma donated from patients who had recovered from H1N1 to severely ill patients with the disease. The treatment markedly reduced their mortality compared to those receiving standard therapy. None suffered any adverse effect from the transfusion.27 Dr. John A. McLean of Australia used this technique for decades to cure typhoid fever.28

Sepsis (or Systemic Inflammatory Response Syndrome)

When limited resources are available to monitor and treat sepsis, such as during epidemics, use the following basic methods, which do not require expensive equipment, to evaluate patients' progress. (Note that the new name for sepsis is systemic inflammatory response syndrome [SIRS].) If a patient fails to improve or deteriorates at any stage, promptly reassess the patient (ABC, history, examination, and so forth). Consider whether the original diagnosis was correct, whether new problems have arisen, and if the current treatment is appropriate. Signs of deterioration may include:

• Persistent or worsening tachycardia
• Persistently elevated or swinging temperature
• Rising white blood cell (WBC) count or C-reactive protein (CRP)
• Falling blood pressure, or increasing vasopressor requirement
• Deteriorating renal output
• Deteriorating level of consciousness
• Deteriorating respiratory function29

Since no scoring system accurately predicts the outcome for individual patients with severe SIRS/sepsis, survival depends on the patient's age, previous health, delay before medical intervention, and medical care provided. In epidemic situations, resources are limited, so physicians must face difficult decisions concerning which patients should receive potentially lifesaving treatments. (An extensive discussion of this is found in the short videos, The Most Difficult Healthcare Decisions, available free [English and Spanish] at http://www.crestaznm.org/crest/ecs/courses/onlineCourses.html?ctid=97 [English].30)

Neglected Tropical Diseases

Eliminating or treating some common tropical diseases may actually be easier than many clinicians think. The "neglected tropical diseases" comprise 17 diseases found in the poorest parts of the world; they afflict 1 billion people. Seven of these diseases—ascariasis, trichuriasis, hookworm infection, schistosomiasis, lymphatic filariasis, trachoma, and onchocerciasis—can be treated (and probably controlled or eliminated if an entire population were to be treated) using a rapid-impact package of drugs. Called "rapid-impact" because community-based workers can quickly distribute them, these drugs result in rapid physical improvements and, in some cases, interruption of disease transmission. These packages include four of six drugs: albendazole or mebendazole, praziquantel, ivermectin or diethylcarbamazine, and azithromycin. They are readily available in many developing countries and generally cost about 50 cents a package, since some of the medications are routinely donated. An additional benefit is that this drug combination also effectively treats scabies, strongyloidosis, pediculosis, tungiasis, and cutaneous larva migrans.31,32