Contagious Period of Viral Diseases
Information about contagious viral infections in the United States, including human papillomavirus (HPV), measles, mumps, and the varicella virus, is explained below. For each virus, the information included details the window of contagiousness, the number of infections in the U.S. in recent years, and the best ways to avoid being infected or spreading the virus once infected.
Human Papillomavirus (HPV)
- According to the CDC, "Human papillomavirus (HPV) is the most common sexually transmitted infection in the United States."
- Because many people who contract HPV do not exhibit noticeable symptoms, it is often difficult to determine when a person was originally infected.
- Most cases of HPV self-resolve within one to two years, but the virus is potentially contagious via sexual intercourse for the entirety of the infection.
- Roughly 14 million people in the U.S. are infected with HPV each year.
- HPV is spread during sexual intercourse, and "can be passed even when an infected person has no signs or symptoms."
- To reduce the chance of an HPV infection, the CDC recommends that people are in a "mutually monogamous relationship" and/or use latex condoms, however, HPC can still be transmitted via areas that a condom does not cover.
- As most sexually active people are likely to be exposed to HPV within their lifetime, the CDC recommends that people are vaccinated between ages 9 through 26 to prevent developing genital warts, cervical precancer, and other HPV-related cancers as a result of being infected with HPV.
Measles Virus (Rubeola)
- Symptoms of measles typically appear 7 to 14 days after infection.
- According to the CDC, "Measles is a highly contagious virus that lives in the nose and throat mucus of an infected person. It can spread to others through coughing and sneezing. Also, measles virus can live for up to two hours in an airspace where the infected person coughed or sneezed."
- Those infected with measles "can spread measles to others from four days before through four days after the rash appears."
- The CDC reported 1,282 cases of measles during 2019 and 12 confirmed cases as of April 5, 2020.
- Two doses of the MMR vaccine, which prevents measles, mumps, and rubella, is on the pediatric vaccine schedule for infants at ages 12 months and 15 months.
- The majority of measles cases are attributable to people who are unvaccinated, which includes infants younger than 12 months, people with allergies to the MMR vaccine, and immunocompromised people, among others.
- Those who are unable to get the MMR vaccine are recommended to make sure all family members have been vaccinated and to avoid public spaces and crowds when possible, and to use a face mask when leaving home.
- Additionally, the CDC states, "If you get MMR vaccine within 72 hours of initially being exposed to measles, you may get some protection against the disease, or have milder illness. In other cases, you may be given a medicine called immunoglobulin (IG) within six days of being exposed to measles, to provide some protection against the disease, or have milder illness."
- Symptoms of mumps, which include fever, headache, aching muscles, tiredness, and loss of appetite, usually appear 16 to 18 days after infection but can also appear 12 to 25 days from infection.
- According to the CDC, mumps "spreads through direct contact with saliva or respiratory droplets from the mouth, nose, or throat. An infected person can spread the virus by coughing, sneezing, or talking; sharing items that may have saliva on them, such as water bottles or cups; participating in close-contact activities with others, such as playing sports, dancing, or kissing."
- The contagious period of mumps lasts from a few days before to five days after the salivary glands of the infected person swell up.
- The CDC reported 70 infections of mumps in the U.S. in January 2020, which is the first time since June 2017 that new outbreaks have been recorded.
- As with measles, an infection of mumps can be prevented by receiving two doses of the MMR vaccine at ages.
- For those who are unable to receive the MMR vaccine, they must also avoid crowds, avoid public events, and wear a face mask when outside the home to avoid being infected with mumps.
- A person that has been infected with the varicella virus will begin to show symptoms of chickenpox from 10 to 21 days after exposure.
- The infected person will be contagious starting 1 to 2 days before the first rash appears to until 24 hours after the last rash appears.
- The CDC estimates that fewer than 350,000 people are infected with the varicella virus each year.
- To avoid contracted chickenpox, the CDC recommends that everyone get two doses of the varicella vaccine, although a small segment of people who are vaccinated will still get a milder version of chickenpox.
- Those who are unable to receive the varicella vaccine due to contraindications in the medical history (i.e. allergy, immunocompromised, etc.) should avoid people who have recently received the varicella vaccine or been exposed to people with chickenpox.
In addition to previous research into chlamydia, influenza A and B, herpes simplex 1 and 2, norovirus, pneumonia, hepatitis C, HIV, strep throat, meningitis, pharyngitis (sore throat), and eye infections, the research team was also tasked with finding a minimum of seven additional contagious viral infections in the U.S. However, we were only able to identify four viruses that fulfilled the criteria. To find viral infections that met the criteria, we searched local, state, and federal infectious disease databases in the U.S., as well as the CDC's current outbreak list. We also searched news databases looking for journal and news articles concerning viral infections in the last several years. We found various viral infections that did not meet the criteria for multiple reasons. The Powassan virus (ticks), the St. Louis encephalitis virus (mosquito), and rabies (animals) are all active in the U.S. but are not normally contagious between humans as they are transmitted via bite. Infections such as rotavirus, adenovirus, and rubella, with which less than 10 people are infected each year, are either not actively tracked or have been effectively eliminated from the U.S. We found several other viruses that are actively infecting humans outside of the U.S., some of which are transmitted via insect bite such as the Zika virus, yellow fever virus, West Nile virus, and others which are transmitted via indirect or direct contact, including the Viral Special Pathogen Branch (Ebola, Seoul Virus, Marburg hemorrhagic fever, Rift Valley fever, hantavirus), typhoid and paratyphoid fever, and Middle East Respiratory Syndrome coronavirus (MERS-CoV), among others.