Here’s what we’ve learned — and what remains unknown

The coronavirus continues to baffle us. Some 100 days after it brought Bay Area life to a standstill — and six months since scientists discovered it — health experts around the world are still scrambling to understand the virus that causes COVID19.

Even as people begin to resume regular life, there is little progress in getting the pandemic under control. There is no vaccine, no proven treatment, and we have no idea what lies ahead.

After months of reporting on the virus, here is what The Chronicle does know.

The virus is still killing thousands of people every day.

While the Bay Area’s aggressive response to the coronavirus pandemic early on helped flatten the curve, case numbers are once again on the rise with the economy reopening, people gathering for largescale protests, and many generally growing restless with stayathome orders.

The Bay Area had 19,072 confirmed cases as of Saturday, including 525 deaths. California now has more than 174,000 confirmed cases, including more than 5,400 deaths. The U.S. has the highest case numbers of any country in the world, with the Centers for Disease Control and Prevention counting a total of more than 2.2 million confirmed cases and more than 119,000 deaths.

“I know people are eager to return to normal activities and ways of life. However, it’s important that we remember this situation is unprecedented, and the pandemic has not ended,” said Dr. Robert Redfield, director of the CDC.

The virus can spread in more ways than we thought.

We know COVID19 is an infectious, respiratory illness that primarily spreads through persontoperson contact when an infected person coughs or sneezes. The CDC has updated its guidelines since March to warn that the virus may also be transmitted by contaminated surfaces, aerosols, and asymptomatic carriers.

“The asymptomatic part is what’s causing this thing to go on,” said Jay Levy, an infectious disease expert at UCSF. “When people are sick, they know it, and they’re going to be in quarantine. But the asymptomatics have a lot of virus and they’re healthy, so they don’t know it.”

You need to wear a mask.

The CDC still recommends the familiar protective measures to help reduce the risk of transmission:

Wear face coverings at all times. Stay 6 feet apart from others when possible.

Avoid physical contact, and don’t shake hands, fistbump or hug.

Wash hands frequently with soap and water, or use alcoholbased sanitizer.

Check out venues ahead of time to make sure they have social distancing protocols in place.

People with any symptoms of illness must stay home.

It affects people of all ages and backgrounds.

Initial reports suggested that those most at risk of becoming seriously ill are over age 50 or have underlying health problems, such as heart disease, lung disease, diabetes or weakened immune systems. Now we know that young adults are equally susceptible to COVID19, with many requiring hospitalization, even intensive care. The majority of coronavirus infections in San Francisco are people in the 18to50 age bracket, according to data collected by the Department of Public Health.

“Everybody is capable of having a severe form of this disease,” said Kirsten BibbinsDomingo, chairwoman of the Department of Epidemiology and Biostatistics at UCSF. “Every age group can end up in the hospital.”

Antibodies may not save you.

One of the most crucial hurdles for immunologists trying to develop a COVID19 vaccine is the question of whether people infected with the virus become immune and, if they do, how long that resistance lasts.

It’s impossible to know whether an individual is safe from the coronavirus based on an antibody test, scientists say, and that may depend on the severity of illness.

“The antibody test can tell an individual potentially whether or not they’ve been infected. But the honest truth is we don’t have enough data to know what that means,” said Bryan Greenhouse, a UCSF associate professor of medicine and a Chan Zuckerberg Biohub investigator who is leading antibody studies in Bolinas and the Mission District of San Francisco.

We don’t know when this is going to be over.

The coronavirus that caused SARS appears to have disappeared about a year after scientists identified it in 2004. That was due to an aggressive global response that placed the affected areas under quarantine. It’s too soon to say what will happen with the coronavirus responsible for COVID19, and the world will need to be on continuous watch until experts develop a vaccine or the virus flames out.

While several drugs are undergoing clinical trials, there is no proof that hydroxychloroquine or any other drug can cure or prevent COVID19. (The most recent treatment that scientists are exploring is dexamethasone.)

Stanford and UCSF researchers believe that the discovery of rare coronavirus antibodies could lead to the development of a vaccine. There are currently 11 candidate vaccines under clinical evaluation and 128 in preclinical evaluation, according to the WHO.

Until one proves effective, we will have to rely on continued testing and contact tracing to control the spread of the virus.