Incubation and Isolation Periods in Common Infections*
| Infection | Incubation Period | Isolation of Patient† |
|---|---|---|
| AIDS | An acute, influenza-like illness may occur 2–4 weeks after exposure to HIV. Antibodies appear within 1–3 months of infection. Clinical AIDS typically develops within 10 years of infection. | Protective isolation if T-cell count is very low; private room only necessary with severe diarrhea, bleeding, copious blood-tinged sputum if patient has poor personal hygiene habits |
| Bloodstream (bacteremia, fungemia) | Variable; usually 2–5 days | |
| Brucellosis | Highly variable, usually 5–21 days; may be months | None |
| Chickenpox | 2–3 weeks | 1 week after vesicles appear or until vesicles become dry |
| Cholera | A few hours to 5 days | Enteric precautions |
| Common cold | 12 hr–5 days | None |
| Covid-19 | 4.5–5.8 days | 5 days if patients are asymptomatic or if their symptoms are resolving (fever-free for 24 hours) |
| Dysentery, amebic | From a few days to several months, commonly 2–4 weeks | None |
| Dysentery, bacillary, e.g., shigellosis | 12–96 hr | As long as stools remain positive |
| Encephalitis, mosquito-borne | 5–15 days | None |
| Giardiasis | 3–25 days or longer; median 7–10 days | Enteric precautions |
| Gonorrhea | 2–7 days; may be longer | No sexual contact until cured |
| Hepatitis A | 15–50 days | Enteric (gloves with infected material; gowns as needed to protect clothing) |
| Hepatitis B | 45–180 days | Blood and body fluid precautions (gloves and plastic gowns for contact with infective materials) |
| Hepatitis C | 14–180 days | As for hepatitis B |
| Hepatitis D | 2–8 weeks | As for hepatitis B |
| Hepatitis E | 15–64 days | Enteric precautions |
| Influenza | 1–3 days | As practical |
| Legionella | 2–10 days | None |
| Lyme disease | 3–32 days after tick bite | None |
| Malaria | 7–10 days for Plasmodium falciparum; 8–14 days for P. vivax, P. ovale; 7–30 days for P. malariae | Protection from mosquitoes |
| Measles (rubeola) | 8–13 days from exposure to onset of fever; 14 days until rash appears | From diagnosis to 7 days after appearance of rash; strict isolation from children under 3 years |
| Meningitis | 2–10 days | Until 24 hr after start of chemotherapy |
| Mononucleosis, infectious | 4–6 weeks | None; disinfection of articles soiled with nose and throat discharges |
| Mumps | 12–25 days | Until the gland s recede |
| Paratyphyoid fevers | 3 days–3 months; usually 1–3 weeks; 1–10 days for gastroenteritis | Until 3 stools are negative |
| Pneumonia, pneumococcal | Believed to be 1–3 days | Enteric precautions in hospital. Respiratory isolation may be required. |
| Puerperal fever, streptococcal | 1–3 days | Transfer from maternity ward |
| Rabies | Usually 2–8 weeks; rarely as short as 9 days or as long as 7 years. | Strict for duration of illness; danger to attendants |
| Rubella (German measles) | 16–18 days with range of 14–23 days | None; no contact with nonimmune pregnant women |
| Salmonellosis | 6–72 hr, usually 12–36 hr | Until stool cultures are Salmonella free on two consecutive specimens collected in 24-hr period |
| Scabies | 2–6 weeks before onset of itching in patients without previous infections; 1–4 days after re-exposed | Patient is excused from school or work until day after treatment |
| Trachoma | 5–12 days | Until lesions disappear, but usually not practical |
| Tuberculosis | 4–12 weeks to demonstrable primary lesion or significant tuberculin reactions | Variable, depending on conversion of sputum to negative after specific therapy and on ability of patient to understand and carry out personal hygiene methods |
* SEE: Stand ard Precautions Appendix.