
Testing of migrant workers returning to Bihar is underlining the twin challenge that public health experts have warned about — the virus is being carried in and many of the carriers are asymptomatic.
Until May 18, Bihar tested a total of 8,337 samples of migrant workers and about 8% were found to be Covid-positive — double the national average positivity rate which is about 4%.
Coronavirus India LIVE Updates
Of the 835 samples taken from migrant workers who returned from Delhi, as many as 218 were Covid positive. This works out to a positivity rate of over 26%, while the rate in the national capital is about 7%.
Incidentally, the count of migrants tested from each state is not proportional to the total number who have returned from that state.
Yet, Delhi is an outlier along with Bengal and Haryana.
Of the 265 samples of migrant workers who returned from West Bengal, 33 tested positive. The positivity rate was 12%, while West Bengal’s positivity rate is 3%.
Read| Testing umbrella to now cover migrants, those in hospitals with symptoms
Of the 390 samples of migrant workers who returned from Haryana, 36 were found to be positive. The positivity rate was 9%, while Haryana’s positivity rate is 1.16%.
The data emerging from Bihar is not only crucial for the state’s containment strategy, but also for the national capital.
Read | 11,000 gather at Ghaziabad for ticket home, 9,000 find a place on six trains
First, it indicates the presence of a large asymptomatic population in Delhi. Second, it can guide the public health authorities in the national capital to carry out contact tracing of these migrants, and contain the spread in areas that may have gone unnoticed.
Migrants returning from other states reported a positivity rate similar to that state’s figure.
So 141 of the 1,283 samples of migrant workers who returned to Bihar from Maharashtra tested positive, showing a positivity rate of 11% (the state’s positivity rate is 11.7%).
Of the 2,045 samples of migrants who returned from Gujarat, 139 tested positive. The positivity rate was 6.8%; it is 7.9% in Gujarat.
Of the 704 samples of migrants who returned from Uttar Pradesh, 21 tested positive. The positivity rate was 3%; it is 2.59% in UP.
Of the 430 samples of migrants who returned from Rajasthan, 16 tested positive. The positivity rate was 3.7%; it is 2.24% in Rajasthan.
Among the southern states, 6 of the 203 samples of migrant workers who returned from Karnataka tested positive. The positivity rate was 3%; it is 0.78% in Karnataka.

Of the 219 samples of migrants who returned from Kerala, 4 tested positive. The positivity rate was 1.8%; it is 1.33% in Kerala.
Of the 57 samples of migrants who returned from Tamil Nadu, 2 tested positive. The positivity rate was 3.5%; it is 3.43% in Tamil Nadu.
However, of the 367 samples of migrant workers who returned from Telangana, 6 tested positive. The positivity rate was 1.6%; it is 6.6% in Telangana.