Sorting precautions: airborne, droplet and contact
Every isolation question begins with one decision: how does this organism travel? Airborne organisms are carried on droplet nuclei small enough to remain suspended and to travel on air currents, so they require a negative-pressure room and a fitted respirator. Droplet organisms travel in larger particles that fall within about two metres, so a private room and a surgical mask suffice. Contact organisms travel by touch, so gown and gloves are the barrier.
Memorise the airborne list because it is short and absolute: tuberculosis, measles, varicella and disseminated herpes zoster. Varicella and disseminated zoster require both airborne and contact precautions because the lesions are infectious to touch. Anything not on the airborne list is not treated with a negative-pressure room, no matter how ill the client appears.
The droplet list includes influenza, pertussis, mumps, rubella, meningococcal meningitis, diphtheria and group A streptococcal pharyngitis. The contact list includes Clostridioides difficile, methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, scabies, impetigo and respiratory syncytial virus. Clostridioides difficile adds a special rule: soap and water handwashing, because alcohol-based rub does not kill the spores.
Standard precautions apply to every client regardless of diagnosis and form the base layer beneath all of the above. Personal protective equipment is applied gown, mask, goggles, gloves, and removed gloves, goggles, gown, mask — with hand hygiene before and after. Removing gloves first is the point most frequently missed.
| Category | Diseases | Room | PPE |
|---|---|---|---|
| Airborne | TB, measles, varicella, disseminated zoster | Negative pressure, door closed | Fit-tested N95 or higher |
| Droplet | Influenza, pertussis, meningococcus, mumps | Private room, door may stay open | Surgical mask within 2 metres |
| Contact | C. difficile, MRSA, VRE, scabies, RSV | Private room preferred | Gown and gloves |
| Contact plus airborne | Varicella, disseminated zoster | Negative pressure | N95 plus gown and gloves |
| Protective / neutropenic | Severe neutropenia, transplant | Positive pressure | Standard PPE; no fresh flowers or raw produce |
Recognising and diagnosing tuberculosis
The classic presentation is a persistent productive cough lasting more than three weeks, sometimes with haemoptysis, accompanied by low-grade afternoon fever, drenching night sweats, unintended weight loss, anorexia and fatigue. Risk factors that push a stem toward tuberculosis include homelessness, incarceration, immigration from a high-prevalence region, HIV infection, immunosuppressive therapy and healthcare work.
The tuberculin skin test is read 48 to 72 hours after intradermal injection, and only induration is measured — redness alone is not counted. The threshold varies by risk group: 5 millimetres for immunocompromised or close-contact clients, 10 millimetres for higher-risk populations, and 15 millimetres for those with no risk factors. A positive result means exposure and sensitisation, not active disease, and it remains positive for life.
Confirmation requires a chest radiograph and sputum specimens for acid-fast bacilli. Sputum is collected in the early morning on three consecutive days, ideally on rising and before eating, because overnight secretions have the highest yield. Interferon-gamma release assays are useful for clients who have received BCG vaccination, because prior BCG causes a false-positive skin test.
Isolation continues until the client has had clinical improvement and three consecutive negative sputum smears collected on different days. That criterion — three negatives on separate days — is a frequently tested detail, as is the fact that the client may be discharged home before the smears convert if the household contacts have already been exposed and adherence is assured.
- •Cough over three weeks plus night sweats plus weight loss
- •Skin test measures induration only, read at 48–72 hours
- •Positive test equals exposure; chest x-ray and sputum confirm disease
- •Early-morning sputum on three consecutive days
- •Isolation lifts after three negative smears plus clinical improvement
The four-drug regimen and its tested adverse effects
First-line therapy uses isoniazid, rifampin, pyrazinamide and ethambutol together for the initial two months, followed by isoniazid and rifampin for at least four more. Multiple drugs are used simultaneously to prevent resistance, and the total duration of six to nine months explains why non-adherence is the leading cause of treatment failure and drug-resistant disease. Directly observed therapy is the standard intervention when adherence is uncertain.
Isoniazid causes peripheral neuropathy by depleting pyridoxine, which is why vitamin B6 is co-prescribed. It is also hepatotoxic, so clients are taught to report jaundice, dark urine, anorexia and right upper quadrant pain, and to avoid alcohol entirely. Rifampin's hallmark is orange-red discolouration of urine, sweat, saliva and tears, which is harmless but permanently stains soft contact lenses; it also induces hepatic enzymes and reduces the effectiveness of oral contraceptives and warfarin.
Pyrazinamide raises uric acid and can precipitate gout, and it is also hepatotoxic. Ethambutol causes optic neuritis, so clients need baseline and periodic visual acuity and colour discrimination testing and must report any blurred vision or change in red-green colour perception immediately. Grouping the adverse effects this way — liver for three of them, eyes for ethambutol, nerves for isoniazid, orange for rifampin — makes the whole regimen memorable.
Client teaching closes most tuberculosis items. Cover the mouth when coughing, dispose of tissues in a sealed bag, use good handwashing, ventilate the home, keep all follow-up appointments, and ensure household contacts are tested. Emphasise that the client will begin to feel better long before the organism is eradicated, and that stopping early is what creates resistant disease.
- •Isoniazid — neuropathy prevented with vitamin B6; hepatotoxic
- •Rifampin — orange fluids; enzyme inducer; contraception counselling
- •Pyrazinamide — hyperuricaemia and gout; hepatotoxic
- •Ethambutol — optic neuritis; check vision and colour discrimination
- •Adherence for six to nine months prevents resistance
How to practise infection control items
Precaution questions are among the most predictable on the exam, which makes them a reliable source of marks. Build a single table of diseases by precaution type, review it briefly every day for a week, and then test yourself with mixed questions rather than rereading the table. Recognition under time pressure is the skill being measured.
Pair this content with the wider infection control material on hand hygiene, sterile technique, sepsis recognition and immunisation, since those areas share vocabulary and reasoning. Our fundamentals question sets and mock exams include precaution items in select-all-that-apply and prioritisation formats with complete rationales.