Open Outbreak

COVID-19

Also known as: SARS-CoV-2, coronavirus disease 2019

COVID-19 is an infectious disease caused by the coronavirus SARS-CoV-2. It mainly spreads through the air when an infected person breathes, talks, coughs, or sneezes, especially indoors and in poorly ventilated spaces. People can spread it before symptoms start, and some people never develop symptoms at all. Illness ranges from no symptoms or a mild cold-like illness to pneumonia, low oxygen, blood clots, and death. Risk is higher in older adults and in people with some medical conditions. Vaccines are available and have been a major tool for reducing severe disease and death. Treatments also exist, including antiviral medicines, but the benefit depends on who is treated and when. Since the start of the pandemic in 2019, the virus has continued to evolve into new variants. WHO said the global emergency phase ended on 2023-05-05, but WHO still assessed the global public-health risk as high in 2025 because the virus continues to circulate and change.

Key facts

TransmissionMainly airborne, including short-range and some longer-range spread indoors; presymptomatic and asymptomatic transmission occurs.
Incubationunknown
Case fatalityunknown; severity varies strongly by age, underlying conditions, immunity, and access to care.
Reproduction numberunknown
VaccineYes. COVID-19 vaccines are available and remain part of WHO guidance.
TreatmentSupportive care and some antivirals are available; remdesivir has been studied extensively, with mixed effects across outcomes in trials reviewed by Cochrane.
ReservoirLikely ultimately animal in origin, with bats often cited in reviews; the exact animal pathway into humans remains uncertain in the sources used here.
Endemic regionsWorldwide

Transmission

COVID-19 spreads mainly through the air. The strongest evidence in the sources used here supports airborne transmission, especially in shared indoor air. Risk is higher in crowded spaces, in places with poor ventilation, and during longer close contact. The evidence also supports some longer-distance indoor spread under the right conditions. This matters because infection is not limited to large droplets falling quickly to the ground. People can also pass the virus on before they feel ill. A living systematic review found that asymptomatic and presymptomatic infections contribute to transmission, which helps explain why outbreaks can grow quickly. For everyday prevention, the same evidence base supports improving ventilation and using well-fitted masks or respirators in higher-risk settings. Transmission patterns can change as new variants appear, so the exact level of risk at a given time depends on what is circulating and how much immunity the population has.

Symptoms and severity

COVID-19 can look very different from one person to another. Some people never develop symptoms. Others get fever, cough, sore throat, runny nose, body aches, tiredness, or loss of smell or taste. In more serious cases, the infection can move into the lungs and cause pneumonia, trouble breathing, and low oxygen levels. Severe illness and death are more likely in older adults and in people with certain health conditions, but serious disease can happen in younger people too. The WHO pandemic page shows the global scale of harm since 2019, with about 770 million reported cases and 7 million deaths in the archived record shown here. Those figures are reported totals, not a fixed fatality rate, and they do not capture all infections. The sources used here do not give one single current case-fatality number that fits all ages, countries, and variants, so that value is best treated as unknown on this page.

Treatment and vaccines

Vaccines against COVID-19 are available and remain central to prevention of severe disease and death. WHO continues to maintain a dedicated COVID-19 vaccines, treatment, and tests programme page, which reflects that these tools are still part of routine public-health management even after the emergency phase ended. Treatment depends on how sick the person is and how early care begins. Supportive care is important for everyone with serious illness, including oxygen and treatment of complications when needed. Antiviral drugs are also used in some settings. One large Cochrane review assessed remdesivir and found that evidence was mixed across outcomes, which is a reminder that treatment effects can depend on timing, disease severity, and the patient group being studied. The sources used here do not provide a single up-to-date WHO summary of all currently preferred medicines, so this page keeps the treatment summary broad rather than overstating certainty.

Where it occurs

COVID-19 now occurs worldwide. It began as a cluster of unexplained pneumonia in late 2019 and then spread across countries within weeks, becoming a pandemic in 2020. The WHO material returned in this session treats COVID-19 as a continuing global health issue rather than a disease limited to a few endemic areas. In the 2025 WHO global situation update, rising activity was reported from sentinel surveillance in several regions, with notable increases in the Eastern Mediterranean, South-East Asia, and Western Pacific regions. That does not mean the virus is absent elsewhere. Instead, it shows that transmission rises and falls at different times in different places. Reviews also describe the virus as a globally transmissible human pathogen. For a general reader, the practical point is simple: exposure is possible in any country, especially during waves of increased community spread, and travel can help move new variants between regions quickly.

Recent history

On this site, the archive count for SARS-CoV-2 is 9 WHO notices or major pandemic records. The WHO items returned here show the early international spread in 2020, including notices for China, Thailand, Japan, and a multi-country event in January 2020. Later in 2020, WHO also posted notices on important variant events, including the United Kingdom variant and mink-associated variant reports from Denmark and multiple countries. The latest WHO Disease Outbreak News item returned here is from 2025-05-28. It says global SARS-CoV-2 activity had been increasing since mid-February 2025 and that test positivity had reached 11%, the highest level seen since 2024-07 in the data available from sentinel sites. The same update said reporting of the variant under monitoring NB.1.8.1 had risen to 10.7% of global sequences by mid-May 2025. WHO’s assessment in that update was that the global public-health risk remained high, even though impacts had declined compared with 2020 to 2023.

What to watch

The main warning signs are changes that suggest the virus is becoming harder to control or more harmful. One is a new variant spreading quickly across multiple regions, especially if WHO starts tracking it closely as a variant under monitoring or higher category. Another is a sharp rise in test positivity, hospital admissions, or deaths after a period of stability. WHO’s 2025 update is a good example of the type of signal public-health teams watch: increasing global activity and a changing mix of variants. Reduced vaccine effectiveness against severe disease would also matter, especially if paired with poor vaccine uptake or supply problems. On the treatment side, any convincing sign that antiviral drugs are working less well would be important. Wastewater surveillance is also useful because it can act as a leading indicator before clinics see the full rise in cases. For the public, the key question is not whether the virus still exists, but whether transmission, severity, or immune escape are starting to climb again.

Updated