You get chickenpox by breathing in virus particles or touching the fluid from an infected person’s blisters. The virus responsible, varicella-zoster, spreads extremely easily through the air and through direct contact, making it one of the most contagious infections a person can encounter. Most people develop symptoms 14 to 16 days after exposure, though the window ranges from 10 to 21 days.
How the Virus Spreads
Varicella-zoster travels primarily through tiny droplets that an infected person releases into the air when they breathe, cough, or sneeze. You don’t need prolonged or close contact to catch it. Simply being in the same room as someone with chickenpox can be enough. The virus can also spread when you directly touch the fluid inside the characteristic blisters.
What makes chickenpox especially hard to contain is that the infected person is contagious before the rash even appears. By the time anyone realizes they’re sick, they may have already been spreading the virus for a day or two. A person remains contagious until every blister has crusted over and dried out, which typically takes five to seven days after the rash starts.
Outside the human body, the virus doesn’t survive long. It typically lasts only a few hours on surfaces and occasionally up to a day or two. This means catching chickenpox from a doorknob or countertop is unlikely. The real risk is person-to-person contact, particularly through the air.
Catching Chickenpox From Shingles
You can also get chickenpox from someone who has shingles, since both conditions are caused by the same virus. This only applies if you’ve never had chickenpox and haven’t been vaccinated. The transmission happens through direct contact with the fluid from shingles blisters or by breathing in virus particles released from those blisters.
There’s an important limit to this risk. People with shingles can only spread the virus while the rash blisters are open and active. Before the blisters appear or after the rash scabs over, they’re not contagious. And unlike chickenpox, shingles itself doesn’t spread. What spreads is the underlying virus, and a newly infected person develops chickenpox, not shingles.
What Happens After Exposure
After the virus enters your body, there’s a quiet period before any symptoms show up. This incubation period averages 14 to 16 days but can range anywhere from 10 to 21 days. During the tail end of this window, you become contagious even though you feel fine and have no visible rash.
In unvaccinated people, the illness follows a familiar pattern: fever followed by an itchy rash that progresses through stages. The blisters appear in waves across the body, and a typical case produces 250 to 500 individual lesions. The whole illness lasts about five to seven days from when the rash first appears to when the last blisters crust over.
Vaccinated People Can Still Get It
Two doses of the varicella vaccine are about 90% effective at preventing chickenpox, which means roughly 1 in 10 vaccinated people can still catch the virus. These “breakthrough” cases look very different from a standard infection. Vaccinated people who get chickenpox typically develop fewer than 50 lesions (compared to 250 to 500 in unvaccinated cases), experience little or no fever, and recover faster. The blisters themselves often look different too, appearing as flat red spots rather than the fluid-filled vesicles of a classic case.
Breakthrough cases are still contagious, though generally less so than a full-blown infection since there are fewer blisters shedding virus.
Can You Get Chickenpox Twice?
It’s commonly believed that chickenpox is a once-in-a-lifetime infection, but second infections do happen and may be more common than most people assume. A surveillance study published by the American Academy of Pediatrics found that 4.5% of reported chickenpox cases in 1995 were in people who said they’d already had the disease. By 1999, that figure had risen to 13.3%. People who had repeat infections were generally healthy, and nearly half reported a family history of repeat infections, suggesting some individuals may be genetically less likely to build lasting immunity.
A second round of chickenpox is typically milder than the first, but it confirms that a previous infection doesn’t guarantee permanent protection for everyone.
What To Do After Exposure
If you’ve been exposed to chickenpox and haven’t been vaccinated, getting the vaccine quickly may still help. Post-exposure vaccination can prevent the illness or significantly reduce its severity if given within the first few days after contact. This is especially relevant for adults, who tend to have more serious cases than children, and for people with weakened immune systems.
For those who’ve already had two doses of the vaccine, no additional action is usually needed after exposure. The existing immunity, even if it doesn’t fully prevent infection, is very likely to keep the illness mild. If you’ve only had one dose, getting the second dose promptly after an exposure provides an important boost in protection.